feat(auth): add STS credential management

[yuxianrz]

Problem

aws-toolkit-vscode does not currently support assume role by inputing user keys (access key and secret key set) and role argument. To keep it consistent with other toolkit IDEs' implementation and give clients a third option to sign in beside SSO and long-term IAM credentials, this feature should be implemented.

Solution

This is part of #7507 and is built on top of #7659.

• Add STS credentials options to LanguageClientAuth requests, including update, invalidate, and cache
• Add STS credentials' role argument input to IAM credentials form to webview
• Modify clients to support IAM and STS credentials

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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