feat(amazonq): Add region profile manager functionality

[opieter-aws]

Problem

The first version of migration of all auth for vscode to Flare using the identity server did not support the recently introduced RegionProfileManager

Solution

These code changes bring back the RegionProfileManager functionality, in the new auth setup. Integration tests and unit tests to be fixed after all references are updated in a follow-up PR to keep the changes manageable. CI is expected to fail.

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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.