feat(amazonq): Migrate existing SSO connections to the LSP identity server

[opieter-aws]

Problem

Existing SSO connections on old auth, are not migrated automatically to the LSP Identity Server. This means that users would be signed out upon migration.

Solution

Add a migration functionality that checks for existing SSO connections, and migrate if necessary:

• Check inside the client.ts, before we attempt to restore any connections in the new auth
• Add migrateSsoConnectionToLsp method to AuthUtil, which:
  • Fetches environment memento, and looks for the auth.profiles key
  • Checks if there is an sso profile with amazonQScopes. If yes: migrate, if not: nothing to migrate
  • [migration]: Update the SSO profile with Flare
  • [migration]: Construct the existing (from) filenames and the Flare (to) filenames for the registration cache file and the SSO token cache file
  • [migration]: rename the files
  • [migration]: set the auth.profiles key to undefined, so migration is skipped next time

Testing

• Covered with unit tests that confirms the actual file system operations
• Manual E2E testing, verifying that there is no sign-out happening with this setup
• We will verify the mechanism through bug bashing

---

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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.
• This pull request implements a feat or fix, so it must include a changelog entry (unless the fix is for an unreleased feature). Review the changelog guidelines.
  • Note: beta or "experiment" features that have active users should announce fixes in the changelog.
  • If this is not a feature or fix, use an appropriate type from the title guidelines. For example, telemetry-only changes should use the telemetry type.

[nkomonen-amazon]

Can we return early if !profiles to reduce indentation depth