Pickle as a default Transformer rather than a special case of function signatures

[elibixby]

TL;DR

Right now only "top level" missing types (those defined directly in a function) are pickled if they don't have a registered TypeTransformer. This PR alters that behavior to anywhere TypeTransformers are used.

Type

• Bug Fix
• [X ] Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

The special casing for pickling as a serialization/deserialization method leads to some strange behavior where, e.g

@task
def my_task(foo: Foo):
   ...

Is valid, because that type is converted, but e.g. Foo inside of a dataclass etc is not. Because the conversion to the placeholder FlytePickle type happens in a function which is only called once on top level type, and only traverses the origin stack, rather than being used anywhere TypeTransformers are used. This PR fixes that problem, while also significantly simplifying the logic to support it.

Tracking Issue

https://github.com/flyteorg/flyte/issues/

Follow-up issue

NA
OR
https://github.com/flyteorg/flyte/issues/

[kumare3]

this seems to be abandoned