Add secret manager block

[ahuang11]

Adds a SecretsManager block, inheriting from the SecretsBlock interface.

Example

Screenshots

Checklist

• References any related issue by including "Closes #" or "Closes ".
  • If no issue exists and your change is not a small fix, please create an issue first.
• Includes tests or only affects documentation.
• Passes pre-commit checks.
  • Run pre-commit install && pre-commit run --all locally for formatting and linting.
• Includes screenshots of documentation updates.
  • Run mkdocs serve view documentation locally.
• Summarizes PR's changes in CHANGELOG.md

[desertaxle]

Does run_sync_in_worker_thread work outside of a flow?

[ahuang11]

Yes it works:

    call = partial(__fn, *args, **kwargs)
    return await anyio.to_thread.run_sync(
        call, cancellable=True, limiter=get_thread_limiter()
    )

[ahuang11]

import anyio
def test():
    print("Hello")
await anyio.to_thread.run_sync(test, cancellable=True)

[desertaxle]

LGTM!