Enable Customer Managed Keys (CMK)

[clearab]

The work would likely involve:

1. Add ability for composer user to turn on the feature and specify the key url
   a. Consider having a key vault key picker (more user friendly but it’s more work)
2. Pass the key url when creating/updating the bot
3. Error handling/surfacing
   a. Failure: invalid key url, missing permissions
   b. If target subscription has policy to disallow non-CMK bot, composer should return a clear error if deployment of a bot fails for that reason
4. Likely want the ability to retrieve the state of CMK for an existing bot to pre-populate the settings (see Update README.md #1 above)
   a. Also consider how conflict between local and remote settings are handled (e.g. does it pick one silently or does it expose the conflict?)
5. Nice to have: do we want to help them with
   a. Create vault/key?
   b. Set up vault permissions (or report on what’s missing)

[clearab]

Closing as duplicate of: #5682