Unify tool functions and user defined functions

[jackgerrits]

Currently, tool functions and user defined functions in executors behave fairly differently. We would like to unify the behavior and usage of these so that they are easier to understand and use.

More details to come in this issue.

[krishnashed]

Hi @jackgerrits I see this github issue is still open and unassigned. I was notified about this issue while working on #1510 by Linxin Song. Can I contribute to this issue ?

[ekzhu]

@jackgerrits is there some advice you can give to @krishnashed regarding this issue?

[jackgerrits]

We need to come up with a plan and design on how to unify them. One option is to add function execution to the code executor interface, another option is to add a FunctionExecutor interface that follows a similar input format to udfs in code executors so they feel consistent.

[rysweet]

all different with 0.4

[jackgerrits]

This one is actually kind of relevant in 0.4 as both features were carried forward