[Feature]: Create drunc endpoint for stopping sessions

### Description

Add a gRPC endpoint in the session manager to tear down an active session.

### Potential impact radius

Small/Isolated

### Reason for change

Progress to being able to launch sessions via the session manager.

### Suggested implementations

gRPC endpoint in `SessionManager` et al.

### Testing suggestions

Can be tested via #661. 

### Anything else?

_No response_