[Core feature] Improved error message with maptasks: using it within a task should error out

[cosmicBboy]

Motivation: Why do you think this is important?

Flytekit should raise a runtime error when map tasks are written in any of the following contexts:

• When a user tries to write a map_task within a task function body

@task
def t1():
    map_task(...)(...)

• When a user tries to define a map_task at the module-level scope

@map_task
@task
def t1(): ...

or

@task
def t1(): ...


my_map_task = map_task()(t1)

Goal: What should the final outcome look like, ideally?

The error should make it clear that map_tasks can only be defined in workflow function bodies.

Describe alternatives you've considered

NA

Propose: Link/Inline OR Additional context

No response

Are you sure this issue hasn't been raised already?

• Yes

Have you read the Code of Conduct?

• Yes

[davidlin20dev]

#take