Add worker commands initial API (#612)

<!-- Describe what has changed in this PR -->
**What changed?**
Add new API for worker commands, and first few commands - Get/Set
Config.
Also add rudimentary config.

<!-- Tell your future self why have you made these changes -->
Part of worker commands work.
We should be able to send commands to the workers/receive response.

<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**
Yep.

<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
[Server PR.](temporalio/temporal#8055)

Author: ychebotarev