New scheduled workflow to test using the azcore backend nightly

[thomas11]

• Initial sketch of using azcore client
• Adjust to recent AzureClient API changes
• Initial implementations of CanCreate, Head, Patch, Post
• Use new azcore client in provider
• TokenCredential bridge: use correct environment
• Use the existing auth stack in the azcore client
• Fix relative URLs and missing API version in Location header for polling
• Fix YAML test program capitalization
• Handle empty PUT body and async polling for completion. TestApi passes.
• Port handling of 404 when polling for deletion
• Upgrade azcore to 1.14
• Fix older bug in CanCreate
• Share code between PUT and PATCH
• Send correct provider version with requests
• Use the correct cloud/environment
• Beginnings of unit testing the new azcore client's HTTP request/response handling
• Add escape hatch to revert to Autorest
• Set Content-Type json header
• Fix some polling-related comments
• Bug fix and tests for CanCreate URL paths
• Set polling frequency to 30s like autorest
• Port handleResponseError
• Verbose request/response logging when log level >= 9
• Configure retries to be more like in Autorest
• Comment on relative Location URLs
• Correctly handle query params
• Remove usage of autorest RequestError in provider
• Propagate azCoreClient creation error; don't create a preliminary AzureClient
• Switch default Azure client to Autorest and add test
• Extend error handling test coverage
• Unit test for HTTP request headers
• Unit tests for CanCreate
• Test that CanCreate uses resource id and path
• Test polling for PUT and PATCH
• Test coverage and fixes for DELETE polling
• Round out test coverage
• comment cleanup
• Prevent double-escaped URL query params
• Some preliminary cleanup
• WIP custom static website, probably using the wrong azblob
• WIP custom static website, using the right azblob, wired up and compiles but untested
• WIP failed attempt to address the 'wrong audience' issue in TestStaticWebsiteDestroyTs
• Revert "WIP failed attempt to address the 'wrong audience' issue in TestStaticWebsiteDestroyTs"
• Beginnings of azidentity auth, CLI so far
• Add some more auth types, beginnings of separate auth config getter
• Check that autorest is enabled for legacy auth
• WIP chained to single credential, parse certs
• New scheduled workflow to test using the azcore backend nightly