This PR is a draft: the relevant changes in MSAL.NET haven't been released yet, and these changes will not work until then.

In MSAL.NET the WithExtraQueryParameters APIs are receiving two changes: AzureAD/microsoft-authentication-library-for-dotnet#5536

• Adding the extra query parameters to the cache keys, so that the correct token can be uniquely found
• Deprecating the existing APIs in favor of one that can allow a customer to control the cache key behavior

This PR is meant to handle the new API and cache behavior. It does so by making changes to the TokenAcquisition class, mainly by adjusting the existing MergeExtraQueryParameters helper method to return the Dictionary style that the new WithExtraQueryParameters API expects.

The changes were tested with a locally built version of MSAL.NET, and all existing tests that dealt with extra query parameters worked with minimal or no changes (in TokenAcquisitionAuthorityTests, ExtraParametersTests, DownstreamApiOptionsMergeTests, and DownstreamApiEndpointTests)