{Core} Add __init__.py to azure.cli.core.sdk

[jiasli]

Description

azure.cli.core.sdk (added by #17671) doesn't have __int__.py, so it will not be included in the whl file, causing CI failure:

https://dev.azure.com/azure-sdk/public/_build/results?buildId=855815&view=logs&jobId=c846b3e8-69b8-5dbd-1a39-4905d81e6a95&j=1e6fba43-bdcf-51f0-a062-3712c33fbb51&t=a1e787eb-ec67-5c3d-79ec-0c68f4f59d65

        # Prepare x-ms-client-request-id header, used by RequestIdPolicy
        if 'x-ms-client-request-id' in cli_ctx.data['headers']:
            client_kwargs['request_id'] = cli_ctx.data['headers']['x-ms-client-request-id']
    
        # Replace NetworkTraceLoggingPolicy to redact 'Authorization' and 'x-ms-authorization-auxiliary' headers.
        #   NetworkTraceLoggingPolicy: log raw network trace, with all headers.
>       from azure.cli.core.sdk.policies import SafeNetworkTraceLoggingPolicy
E       ModuleNotFoundError: No module named 'azure.cli.core.sdk'

This is because setup.py uses find_packages to find packages to include in the whl file:

azure-cli/src/azure-cli-core/setup.py

Line 91 in 6728379

packages=find_packages(exclude=["*.tests", "*.tests.*", "tests.*", "tests", "azure", "azure.cli"]),

Only folders with __int__.py are marked as a package.

Similar problem happened before: #15711 (comment).

[yonzhan]

Core

[yonzhan]

LGTM