Add method to print TLM model name

[huiwengoh]

Adds new method get_model_name() to easily know which model the TLM is using.

I've also explicitly specified which default model is being used in the client API call to the backend. Currently, if no model is specified from the client, we use the default in the backend but this get_model_name() method can get outdated if someone uses an older version of the client library against an updated backend.

Sample usage:

tlm = studio.TLM()
tlm.get_model_name()

>> 'gpt-4o-mini'

tlm = studio.TLM(options={"model": "claude-3-haiku"})
tlm.get_model_name()

>> 'claude-3-haiku'

tlm_hybrid = studio.TLMHybrid()
tlm_hybrid.get_model_names()

>> {'response_model': 'gpt-4o', 'score_model': 'gpt-4o-mini'}

[jwmueller]

LGTM, just had minor suggestion