* update arch docs; remove old EvalNode and EvalTree references

Revert "match terraform-releases expectations"

This reverts commit 270de49e.

match terraform-releases expectations

remote provisioners require a connection config

objchange: catch invalidly planned attributes earlier

cli: Remove -var/-var-file flags from validate

As usual, we'll continue to iterate on this based on feedback and
questions during the beta period, but this is a first draft intended to
help those who are trying out the first beta.

These flags are not used and have been deprecated since 0.12.11.

this fixes a bad merge on my part 

Catch attributes which are planed but not computed separately to provide
a clearer error to provider developers.

The error conditions were previously caught, however it was unclear from
the error text as to _why_ the change was an error. The statements about
value inequality would be incorrect when planning no changes for a value
which should not have been set in the first place.

* providers.Interface: rename ValidateDataSourceConfig to
ValidateDataResourceConfig

This PR came about after renaming ValidateResourceTypeConfig to
ValidateResourceConfig: I now understand that we'd called it the former
instead of the latter to indicate that the function wasn't necessarily
operating on a resource that actually exists. A possibly-more-accurate
renaming of both functions might then be ValidateManagedResourceConfig
and ValidateDataResourceConfig.

The next commit will update the protocol (v6 only) as well; these are in
separate commits for reviewers and will get squashed together before
merging.

* extend renaming to protov6

* Update Godoc links from godoc.org to pkg.go.dev

* Update reference to renamed GraphNodeResource interface

Ref hashicorp/terraform#24389

* Update dead links; minor formatting adjustments

* Add FIXME item following deprecation of EvalNode

cli: Add reference to global options to help text

Document `inline` & `on_failure` behaviour

Add State Learn tutorial to State docs

jsonstate: indicate schema version mismatch during encoding

Although we don't typically do configuration-level string wrangling
directly in Terraform, we delegate to several other upstream libraries
that do. These upgrades all switch to newer versions that support the
latest definitions from Unicode 13, primarily affecting operations such
as converting strings to upper/lowercase or splitting strings into
component characters (substr, reverse, etc).

The tests for the upstream libraries didn't show any regressions from
these updates, so the Unicode 13 changes seem to be backward-compatible
additions rather than significant breaking changes.

(Our go.mod file had also become non-canonical in some ways, and the Go
toolchain fixed that as part of this work, causing a few extra style-only
diffs here that shouldn't cause any change in behavior.)

Provider transformer cleanup

Instead of returning an error with no context about unexpected
attributes or incorrect types, notify users that the schema stored in
the state does not match the current provider.

User can only encounter this error if the providers have updated their
schemas since the state was stored. This would appears when running
`terraform show -json` to display the current state, or
`terraform show -json planfile` if that plan was created with
`-refresh=false`. In either case, the state must be refreshed in order
to properly json encoded.

cli: Migrate plan to command views

The auto-approve argument was part of the arguments.Operation type,
which resulted in adding a silent -auto-approve flag to plan and
refresh. This was unintended, and is fixed in this commit by moving the
flag to the arguments.Apply type and updating the downstream callers.

cli: Migrate refresh to command views

Since this is still at an early phase and likely to change significantly
in future iterations, rather than attempting to guess on a suitable final
location for documenting the testing feature I've instead taken the
unusual approach of adding a new page that is explicitly about the
experiment. My expectation is that once we conclude the experiment we'll
replace this new page with a stub that just explains that there was once
an experiment and then links to whatever final feature unfolded from the
research.

The URL for this page is hard-coded into the warning message in the
"terraform test" command, so as we continue to evolve this feature in
future releases we'll need to update the callout note on the page about
which Terraform CLI version it's currently talking about, so users of
older versions can clearly see when they'd need to upgrade in order to
participate in a later incarnation of the experiment.

This is just a prototype to gather some feedback in our ongoing research
on integration testing of Terraform modules. The hope is that by having a
command integrated into Terraform itself it'll be easier for interested
module authors to give it a try, and also easier for us to iterate quickly
based on feedback without having to coordinate across multiple codebases.

Everything about this is subject to change even in future patch releases.
Since it's a CLI command rather than a configuration language feature it's
not using the language experiments mechanism, but generates a warning
similar to the one language experiments generate in order to be clear that
backward compatibility is not guaranteed.

As part of ongoing research into Terraform testing we'd like to use an
experimental feature to validate our current understanding that expressing
tests as part of the Terraform language, as opposed to in some other
language run alongside, is a good and viable way to write practical
module integration tests.

This initial experimental incarnation of that idea is implemented as a
provider, just because that's an easier extension point for research
purposes than a first-class language feature would be. Whether this would
ultimately emerge as a provider similar to this or as custom language
constructs will be a matter for future research, if this first
experiment confirms that tests written in the Terraform language are the
best direction to take.

The previous incarnation of this experiment was an externally-developed
provider apparentlymart/testing, listed on the Terraform Registry. That
helped with showing that there are some useful tests that we can write
in the Terraform language, but integrating such a provider into Terraform
will allow us to make use of it in the also-experimental "terraform test"
command, which will follow in subsequent commits, to see how this might
fit into a development workflow.

cli: Migrate apply to command views