Refine #15184: {Core} Honor scopes specified by Track 2 SDK

Expected flow

The current Track 2 SDK client takes credential_scopes with only one resource as the scopes when calling get_token.

https://github.com/Azure/azure-sdk-for-python/blob/27e4203818e227ba2604ff52dcf55ce2293c4c37/sdk/resources/azure-mgmt-resource/azure/mgmt/resource/subscriptions/_configuration.py#L60

self.authentication_policy = policies.BearerTokenCredentialPolicy(self.credential, *self.credential_scopes, **kwargs)

Issue 1: Empty scopes

Some old Track 2 SDKs generated before Azure/autorest.python#239 don't maintain credential_scopes and calls get_token with an empty scopes.

https://github.com/Azure/azure-cli-extensions/blob/db8ea65eb4afa9358de39e06a8c37c85e862a61c/src/datashare/azext_datashare/vendored_sdks/datashare/_configuration.py#L61

https://github.com/Azure/azure-cli-extensions/blob/db8ea65eb4afa9358de39e06a8c37c85e862a61c/src/logic/azext_logic/vendored_sdks/logic/_configuration.py#L61

self.authentication_policy = policies.BearerTokenCredentialPolicy(self.credential, **kwargs)

This causes error:

File "/opt/hostedtoolcache/Python/3.6.12/x64/lib/python3.6/site-packages/azure/cli/core/util.py", line 1196, in scopes_to_resource 
scope = scopes[0] 
IndexError: tuple index out of range 

Issue 2: Multiple scopes

Some old Track 2 SDKs generated before Azure/autorest.python#745 extend default credential_scopes with custom credential_scopes. Instead, credential_scopes should be replaced by custom credential_scopes. Azure/azure-sdk-for-python#12947

https://github.com/Azure/azure-cli-extensions/blob/120196e953f7b776fa209f4c49838b5cc7af56b0/src/account/azext_account/vendored_sdks/subscription/_configuration.py#L44-L45

self.credential_scopes = ['https://management.azure.com/.default']
self.credential_scopes.extend(kwargs.pop('credential_scopes', []))

Changes

This PR unifies the fixes for the above 2 issues in one function _try_scopes_to_resource:

Testing Guide

# Test empty scopes
> az extension add --name datashare
> az datashare account list --debug
DEBUG: AdalAuthentication.get_token invoked by Track 2 SDK with scopes=()
DEBUG: No scope is provided by the SDK, use the CLI-managed resource.

# Test multiple scopes
> az extension add --name account
> az account subscription show --id 0b1f6471-1bf0-4dda-aec3-cb9272f09590 --debug
DEBUG: AdalAuthentication.get_token invoked by Track 2 SDK with scopes=('https://management.azure.com/.default', 'https://management.core.windows.net//.default')
DEBUG: Multiple scopes are provided by the SDK, discarding the first one: https://management.azure.com/.default

⚠ The workarounds only work for now as get_token is implemented by Azure CLI. After migrating to Azure Identity, these workarounds will fail. The old problematic SDKs MUST be regenerated.