VSCodeCredential Improvements for Copper

[joshfree]

For Copper we are removing VisualStudioCodeCredential from DefaultAzureCredential's credential chain. In a future semester we intend to fix it and restore it.

• Remove VisualStudioCodeCredential from DefaultAzureCredential
• Ensure troubleshooting guides recommend users use the Azure CLI to log in for developemnt time scenarios
• Ensure any logging or exception text no longer references VisualStudioCodeCredential in the DefaultAzureCredential path
• Update README to include notification that this change has occurred

Related:

• https://docs.microsoft.com/azure/developer/java/sdk/identity-dev-env-auth#visual-studio-code-credential
• [Identity] Getting a token via VisualStudioCodeCredential using v0.10.0 of the Azure Account Extension results in an error #23249

[billwert]

Addressed by #25493. Error messages already had links to TSG.