[tsp-client] Error out when emitter-output-dir is not set for the running language?

It would be nice if tsp-client could throw an error when the `emitter-output-dir` is not set.
When generating packages into the SDK repo, the directory structure is important. If this value is not set, code will be generated into the default directory, which is something like `/tsp-output`.
Some users see the code was generated into a wrong location, they would just move them into the correct place without letting the reviewers know about this.
This breaks all the process in the SDK repo.
An example here: https://github.com/Azure/azure-sdk-for-net/pull/54644/changes/f09eea4b8be8b8420c7c2d3d8a70f7f002aec54b#diff-eb1639b7cbcdb87e3455d1a52818471751faaa1429a8ae4a6eee970a2a0dda66

Start at the tsp-client entry point that handles emitter-output-dir and reproduce package generation with the value unset. Trace where the default /tsp-output location is selected; done means the client reports an error instead of generating into that default directory.

Written by the indexing model from the issue text.