feat(auth): add IAM credentials LSP requests to AuthUtils and auth2

[liramon1]

Problem

The authentication flow does not make requests to IAM credentials endpoints on Flare and does not provide places for clients to input long-term IAM credentials or STS credentials.

Solution

• Add IAM and STS credentials options to LanguageClientAuth requests
• Add IAM credentials option and form to webview
• Modify AuthUtils to switch between SsoLogin and IamLogin strategies
• Modify clients to support IAM and STS credentials
• Add IAM and STS credentials unit tests

This feature is split into multiple PRs (in order):

1. feat(auth): add support for IAM profile management and flare endpoints #7659
2. feat(auth): add STS credential management #7661

Meanwhile, we are making changes to language-servers and language-server-runtimes such that authentication for IAM credentials can happen on Flare side.

Tests will work with this version of language-server-runtimes:
https://github.com/liramon1/language-server-runtimes/tree/feature/flare-iam

and this version of language-servers:
https://github.com/liramon1/language-servers/tree/liramon/flare-iam

Please reference these when reviewing our work

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License

I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

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