Support auto-loading appropriate ims context based on program id mapping

Currently only one Adobe IO JWT can be stored inside the aio config (because only the key `jwt-auth`) is used. For working with multiple accounts in parallel it would be beneficial if multiple JWT authentication configs could be stored in parallel and bound to specific Cloud Manager Program ID.
Maybe supporting a key config naming scheme like `jwt-auth.` would be sufficient. If no such key is found, the fallback could be the key `jwt-auth`.

Start by locating where the aio config reads the jwt-auth key and where the Cloud Manager program ID is available. Verify the proposed jwt-auth. lookup with jwt-auth fallback, while keeping multiple accounts usable in parallel; add or update tests for both selection paths.

Written by the indexing model from the issue text.