{KeyVault} Replace _token_retriever with get_raw_token

[jiasli]

Split from #17738

Description

As pointed out by #15854, calling the protected method _token_retriever is simply wrong.

This PR replaces _token_retriever with azure.cli.core._profile.Profile.get_raw_token, as provided by #15805 (comment).

This is also the approach adopted by azure.cli.command_modules.keyvault._client_factory.keyvault_data_plane_factory:

azure-cli/src/azure-cli/azure/cli/command_modules/keyvault/_client_factory.py

Lines 128 to 137 in 1eed077

	def keyvault_data_plane_factory(cli_ctx, _):
	from azure.keyvault import KeyVaultAuthentication, KeyVaultClient
	from azure.cli.core.util import should_disable_connection_verify
	version = str(get_api_version(cli_ctx, ResourceType.DATA_KEYVAULT))
	def get_token(server, resource, scope): # pylint: disable=unused-argument
	import adal
	try:
	return Profile(cli_ctx=cli_ctx).get_raw_token(resource)[0]

On the other hand, instead of implementing its own keyvault client factory, appconfig directly uses azure.cli.command_modules.keyvault._client_factory.keyvault_data_plane_factory (#15826):

azure-cli/src/azure-cli/azure/cli/command_modules/appconfig/_kv_helpers.py

Lines 300 to 301 in 7a5538f

	from azure.cli.command_modules.keyvault._client_factory import keyvault_data_plane_factory
	keyvault_client = keyvault_data_plane_factory(cli_ctx, None)

Other command modules may follow the same approach, but I will defer this decision to @houk-ms.

[jiasli]

This _get_token never works because it doesn't comply with KeyVaultAuthentication's authorization_callback signature.

Also defer to @houk-ms to fix it in the future.

[qwordy]

How about put _get_token to azure-cli-core?

[qwordy]

Can we make Profile object a global singleton?

[jiasli]

Good suggestion. Will consider doing that in the future.

[houk-ms]

How about put _get_token to azure-cli-core?

We will consider to do that when KeyVault data-plane SDK decides to migrate to Track2. Before that, i prefer we keep the original implementation for simplicity.