feat: add stream endpoint

[bwanglzu]

Finetuner-API now supports a new endpoint: /logstream, in this PR we allow the client to subscribe this endpoint.

import finetuner

finetuner.login()

run = finetuner.get_run(
    run_name='log-streaming-exp-run-7',
    experiment_name='log-streaming-exp'
)

for log_entry in run.stream_logs():
    print(log_entry)

---

• This PR references an open issue
• I have added a line about this change to CHANGELOG

[jupyterjazz]

Looks good!

Just one comment:
It looks like this is the only intended way of getting the logs:

for log_entry in run.stream_logs():
    print(log_entry)

so why not combining it into run.logstream() or something?

[bwanglzu]

@jupyterjazz we'll discuss tomorrow when @gmastrapas is back

[gmastrapas]

LGTM!