Unify the query execution logic across all modes (interactive, headless)

[ybyzek]

Unify the query execution logic across interactive mode, non interactive mode, and RUN SCRIPT.

This issue is desirable as it relates to:
#1031
#1320

[apurvam]

@big-andy-coates assigning this to you since you are already looking into this problem. It would be good to unify the behavior of multiline statements across modes as well. Right now, I think they are supported in the CLI, but what about in run script and in non-interactive mode?

[miguno]

Also, @hjafarpour recently completed Sync Application(headless) mode behavior with the interactive mode. #1599. Has that PR improved the situation described in this ticket? For example, that PR fixed #1320, which @ybyzek referred to in her original message at the very top here.

Lastly, there is the related ticket Avro limitation for commands in run script versus interactive #1031 -- similar to @apurvam's comment above about RUN SCRIPT.

[big-andy-coates]

This is done now. The only piece of the puzzle left to do is proper support for schema inference in headless mode, i.e. storing the KSQL schema somewhere so things do not get messed up if schemas evolve in the schema registry.