[Task]: [RRIO] [Cache] Write transform

[damondouglas]

The output of this task is a Cache Write transform that transforms a PCollection of element KVs and writes the pair to an external resource, persisting their association. Re-uses the Call PTransform and therefore serves as a dependency.

Measures of Ready

• [Task]: [RRIO] [Call] PTransform executes user custom code without adaptive throttling #28711

Measures of Done

• Write operations are not coupled with the transforms DoFn but rather provided through an interface
• Tests validate that matching elements persist and are retrievable in the same state association

Issue Priority

Priority: 2 (default / most normal work should be filed as P2)