Test migration to MCS SDK (DO NOT MERGE)

[tracyboehrer]

Not complete:

1. Custom User-Agent
2. Connector Request headers
3. Few unit tests need correction
4. Unclear how TeamsAttachmentDownloader is created, but it now requires IGetCopilotAccessToken
5. Removed default constructor for TeamsAdapter. Needs follow up concerning unit tests.
6. During forking, appear to have trampled a change to FilteredTeamsSSOTokenExchangeMiddleware and OAuthBotAuthentication that happened on main

I don't recommend using this PR. Should likely only take a couple hours to redo when ready + additional testing.

[corinagum]

@tracyboehrer For extra assurance, would you mind turning this PR into a draft PR? Thank you!