Duplicate RPC names aren't detected, but stop the RPC server from booting up.

I recently had to manually debug a case where I'd added a duplicate RPC name. The error I got when doing this is a generic server protocol error, as follows:

```mobly.snippet.errors.ServerStartProtocolError: INSTRUMENTATION_RESULT: shortMsg=Process crashed. ```

As my team is planning to add many new RPCs to our local copy of this snippet, it might prevent alot of headache if this particular error could be detected or flagged with a clearer error message, identifying (or at least mentioning) the duplicate RPC name. Is this possible to implement?

No file or test is identified in the issue. Start by tracing RPC registration and server startup to find where duplicate names are accepted; done means duplicate RPC names are rejected or reported with the conflicting name instead of only producing the generic server protocol error.

Written by the indexing model from the issue text.