Move the S3 State from a legacy remote state to an official backend.

This increases test coverage, uses a set schema for configuration, and
will allow new backend features to be implemented for the S3 state, e.g.
"environments".

ignore_changes causes keys in other flatmapped objects to be lost from diff

When transforming a diff from DestroyCreate to a simple Update,
ignore_changes can cause keys from flatmapped objects to be filtered
form the diff. We need to filter each flatmapped container as a whole to
ensure that unchanged keys aren't lost in the update.

* add option zone_id

- Ref: http://docs.idcf.jp/cloud/api/address/#listpublicipaddresses

* Exclusion of `network_id`, `vpc_id` and `zone_id`

* Revert "Exclusion of `network_id`, `vpc_id` and `zone_id`"

This reverts commit 9684c8b0b65b3353aea4e0bfbeaf21986282812b.

* remove zone_id from one of required option.

ignore_changes is causing changes in other flatmapped sets to be
filtered out incorrectly.

This required fixing the testDiffFn to create diffs which include the
old value, breaking one other test.

Many cloud services prevent duplicate key pairs with different names.
Among them are Digital Ocean, Joyent Triton and Packet. Consequently, if
tests leave dangling resources it is not enough to simply randomise the
name, the entire key material must be regenerated.

This commit adds a helper method that returns a new randomly generated
key pair, where the public key material is formatted in OpenSSH
"authorized keys" format, and the private key material is PEM encoded.

command: remove legacy remote state on migration

* add nil check when assingment from a doc parameter to the param map

* remove println

Fixes #12871

We were forgetting to remove the legacy remote state from the actual
state value when migrating. This only causes an issue when saving a plan
since the plan contains the state itself and causes an error where both
a backend + legacy state exist.

If saved plans aren't used this causes no noticable issue.

Due to buggy upgrades already existing in the wild, I also added code to
clear the remote section if it exists in a standard unchanged backend

[DOCUMENTATION] Change version of Debian image

* provider/aws: Added Usage Plan Key resource

* provider/aws: Added usage plan import documentation

The -u flag didn't work for me and based on documentation should be -update, which did work.  Makes getting started docs more accurate.

Adds support for `name_prefix` to the `aws_autoscaling_group` and `aws_elb` resources. Unfortunately when using `name_prefix` with `aws_elb`, this means that the specified prefix can only be a maximum of 6 characters in length. This is because the maximum length for an ELB name is 32 characters, and `resource.PrefixedUniqueId` generates a 26-character unique identifier. I was considering truncating the unique identifier to allow for a longer `name_prefix`, but I worried that doing so would increase the risk of collisions.

provider/aws: Fix flattened cloudfront lambda function associations to be a set, not a slice (#11984)

* Validate credentials

* Add ability to skip validation

* Update provider documentation

* invalidCredentials -> invalidCreds

* Include original error message

* Update description for skip_credentials_validation

* Add config test

* set skip_credentials_validation default to false