App Config Provider Connection String to Entra ID testing

[mrm9084]

Description

Moves testing of the provider from connection string to entra id.

[Copilot]

Pull request overview

This PR consolidates provider integration testing onto Entra ID (AAD) authentication by switching tests from using an App Configuration connection string to using the App Configuration endpoint + credential flow, and removes the now-redundant AAD-specific test modules.

Changes:

• Updated sync and async provider tests to use endpoint=... instead of connection_string=....
• Removed separate AAD test files after folding their coverage into the main test modules.
• Updated live-only test resource setup to use devtools_testutils.get_credential() instead of DefaultAzureCredential.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
sdk/appconfiguration/azure-appconfiguration-provider/tests/test_provider.py	Migrates provider integration tests to endpoint-based auth (Entra ID) and keeps related unit-style tests (e.g., content-type processing).
sdk/appconfiguration/azure-appconfiguration-provider/tests/aio/test_async_provider.py	Migrates async provider integration tests to endpoint-based auth and adds additional tag-filter assertions.
sdk/appconfiguration/azure-appconfiguration-provider/tests/conftest.py	Uses get_credential() for live-only App Config setup instead of instantiating DefaultAzureCredential directly.
sdk/appconfiguration/azure-appconfiguration-provider/tests/test_provider_aad.py	Deleted (coverage moved into test_provider.py).
sdk/appconfiguration/azure-appconfiguration-provider/tests/aio/test_async_provider_aad.py	Deleted (coverage moved into test_async_provider.py).