Add snippet updater to azpysdk

[jenny (JennyPng)]

closes #45007

• add update_snippet to azpysdk
  https://github.com/Azure/azure-sdk-for-python/blob/main/eng/tools/azure-sdk-tools/ci_tools/snippet_update/python_snippet_updater.py

• remove original script and tests

• update snippet depends on proper black format being applied to samples

• refactor black.py to have black running logic be reusable

• run black in update_snippet

• move tests for update_snippet

• update snippet docs

pipelines

core: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=5864413&view=logs&j=36df4387-3551-57fa-098c-b43a23930261&t=2cab49f9-f561-5eca-3dcd-aa98c816598e&s=ff05ad62-bb9a-53b6-ce9f-72f329a63e7c
storage: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=5880152&view=logs&j=b70e5e73-bbb6-5567-0939-8415943fadb9&t=0a38c4fb-2772-5578-aac2-81402a187585

next step

• azsdk mcp/cli uses the old update_snippet script, need to update that

[Copilot]

Pull request overview

This PR migrates the Python README snippet updater into the azpysdk CLI, refactors the black check to expose reusable formatting logic, and updates CI/pipeline wiring and documentation to use the new command.

Changes:

• Add azpysdk update_snippet command (with optional --no-black) and new unit tests under azpysdk/tests.
• Refactor azpysdk black to reuse a shared format_directory implementation.
• Update pipeline step/template and docs to invoke snippet updates via dispatch_checks.py / azpysdk.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
eng/tools/azure-sdk-tools/azpysdk/update_snippet.py	New azpysdk check to extract snippets and sync them into README files (and optionally run black).
eng/tools/azure-sdk-tools/azpysdk/tests/test_update_snippet.py	New unit tests for snippet extraction and README updating.
eng/tools/azure-sdk-tools/azpysdk/tests/init.py	Adds azpysdk tests package marker.
eng/tools/azure-sdk-tools/azpysdk/main.py	Registers the new update_snippet subcommand in the CLI.
eng/tools/azure-sdk-tools/azpysdk/black.py	Refactors black invocation into a reusable format_directory helper.
eng/pipelines/templates/steps/update_snippet.yml	Switches snippet update execution to dispatch_checks.py running the update_snippet check.
eng/pipelines/templates/steps/analyze.yml	Passes through updated parameters for the new snippet update template.
doc/tool_usage_guide.md	Documents the new azpysdk update_snippet command.
doc/dev/code_snippets.md	Updates snippet-maintenance instructions to use azpysdk update_snippet.
eng/tools/azure-sdk-tools/ci_tools/snippet_update/python_snippet_updater.py	Removes the legacy snippet updater script.
eng/tools/azure-sdk-tools/tests/test_python_snippet_updater.py	Removes legacy tests for the old updater.
eng/tools/azure-sdk-tools/ci_tools/snippet_update/test_python_snippet_updater.py	Removes legacy tests for the old updater.

[Scott Beddall (scbedd)]

This looks like a solid update jenny (@JennyPng) .

I did agree with the copilot comment for paranoia's sake, but the regex does handle it so it's just an extra check.