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 Since run command is a legacy, it has arbitrary or outdated option names such as mode or type - they both has a same choice named batch.-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.
This should be rather a refactoring of the run command and a follow-up of #283.
Let's rename the existing run command to run-legacy, and write the new run() using start and exec combinations from a clean slate.