command/init: Add -cloud alias to -backend, adjust `init` help output

Cloud integration requires input for migrations

We cannot programmatically migrate workspaces to Terraform Cloud without
prompts, so `-input=false` should not be allowed in those cases.

There are 4 scenarios where we need input from a user to complete
migrating workspaces to Terraform Cloud.

1.) Migrate from a single local workspace to Terraform Cloud

* Terraform config for a local backend. Implicit local (no backend
  specified) is fine.
* `terraform init` and `terraform apply`
* Change the Terraform config to use the cloud block
* `terraform init -input=false`
* You should now see an error message

2.) Migrate from a remote backend with a prefix to Terraform Cloud with
  tags

* Create a workspace in Terraform Cloud manually. The name should
  include a prefix, like "app-one"
* Have the terraform config use `backend "remote"` with a prefix set to
  "app-"
* `terraform init` and `terraform apply`
* Update the Terraform config to use a cloud block with `tags
  = ["app"]`. There should not be a prefix defined in the config now.
* `terraform init -input=false`
* You should now see an error message

3.) Migrate from multiple local workspaces to a single Terraform Cloud
  workspace
* Create one or many local workspaces
* `terraform init` and `terraform apply` in each
* Change the Terraform config to use the cloud block
* `terraform init -input=false`
* You should now see an error message

4.) Migrate to Terraform Cloud and ask for a workspace name
* Create several local workspaces
* `terraform init` and `terraform apply` in each
* Change the Terraform config to use the cloud block with tags
* `terraform init -input=false`
* You should now see an error message

Revert "migrate docs to mdx"

This reverts commit 3cb12b5a.

Create a function for logic that assigns value to initReason var after changing backend configuration (#29967)

* Create a function for logic that assigns value to initReason var after changing backend configuration

Create func determineInitReason() for logic block that assigns value to initReason var after changing backend/cloud configuration block or migrating to a different type of backend configuration. Also clarify 'cloud' configuration block message to say 'Terraform Cloud configuration block has changed' instead of 'Terraform Cloud configuration has changed'.

cli: Fix nested single and map diff rendering

Indentation was out by two spaces. This is now consistent with the other
displays of object/map values: four spaces for each nesting level.

Some of the wording here needed adjusting with the change that backends
largely reflect state snapshot storage (removing 'enhanced'
designation), and that a 'backend' is not necessarily always present.

This fixes an issue where a user could not disable initialization of the
'cloud' configuration block (As is possible with -backend=false), as
well as add some syntactic sugar around -backend by adding a mutually
exclusive -cloud alias.

cli: Fix diff for nested set unchanged elements

Unchanged elements in nested attributes backed by sets were previously
misrendered as empty objects. This commit removes the additional
brackets and adds a count of unchanged elements.

Fix failing checks

* Remove double question to migrate
* Remove parallelism (it has been flaky)
* Add subtests to apply_auto_approve_test (it was overlooked before)

The specialized Terraform Cloud migration process asks right up top
whether the user wants to migrate state, because there are various other
questions contingent on that answer.

Therefore we ought to just honor their earlier answer when we get to the
point of actually doing the state migration, rather than prompting again.

This is tricky because we're otherwise just reusing a codepath that's
common to both modes. Hopefully we can find a better way to do this in
a later commit, but for the moment our main motivation is minimizing risk
to the very next release.

There are a few command line options for "terraform init" which are only
relevant when working with traditional backends, with the Cloud
integration previously just mostly ignoring them, or sometimes misbehaving
slightly due to them creating an unreasonable situation.

Now we'll catch these and return explicit errors, in order to be clear
that these options are not needed nor supported in Cloud mode.

This just gives a little extra information to work with when trying to
understand why a test failed. It doesn't change what any of the tests are
actually trying to test.

This aims to encapsulate the somewhat-weird logic we currently use to
distinguish between the various "terraform init" situations involving
Terraform Cloud mode, in the hope of making codepaths that branch based
on this slightly easier to read.

This isn't yet used, but uses of it will follow in subsequent commits.

This PR adds support for using MSAL instead of ADAL for getting auth tokens in the AzureRM backend, meaning that Microsoft Graph Tokens will be used rather than Azure Active Directory Graph Tokens.

For the moment this is an opt-in feature - however in a future release we'll flip the default from ADAL to MSAL since ADAL is deprecated.

Co-authored-by: Tom Bamford <tbamford@hashicorp.com>

Co-authored-by: Tom Bamford <tbamford@hashicorp.com>

Co-authored-by: Tom Bamford <tbamford@hashicorp.com>

Co-authored-by: Tom Bamford <tbamford@hashicorp.com>

Co-authored-by: Tom Bamford <tbamford@hashicorp.com>

This redirects to the registry so we should point there directly

Remove retracted k8s package