Refactor `run` command to be a combination of `start` and `exec` commands

**Is your feature request related to a problem? Please describe.**`client-py` has 2 short-cut commands `run` and `start`, which can create new session. Since `run` command is a legacy, it has arbitrary or outdated option names such as `mode` or `type` - they both has a same choice named `batch`.-

\*Describe the solution you'd like\*implement `execute` command and change `run` command into a combination of `start` and `execute`.

**Additional context**`run` command was implemented to execute python codes.The code can be sent through API by string format or through uploading a file.

JIRA Issue: BA-267