Squashed work of AWS support.

[BigTailWolf]

• feat: Add External Account Credential support as well as support for impersonated credential

• chore: Add tests for ExternalAccount, add methods required to make test compatible with apply_auth_examples. ExternalAccount was not fully compatible with the other providers, this brings it in line and moves some common methods between the other provides and ExternalAccount into a module which is now included by the AWSClient provider and Signet::Auth::Client

• chore: Move AWS Credentials to their own file, do not pass role from external account, create dedicated Connection helper module, other misc PR cleanup

• chore: Update BaseClient documentation comment

• chore: Ensure the subject token type matches AWS before building AwsCredentials

• feat: perform validation and add tests

• Fixes to get manual testing working

• dates

• fixes

• Allow different versions of Faraday

• ALlow different versions of Faraday

• chore: use SampleLoader for running sample tests (#411)

• address the comments

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[conventional-commit-lint-gcf[bot]]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot https://conventionalcommits.org/

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