Describe the bug
Post steps in of nested composite actions have the wrong context. It's the context of the parent that is used instead of it's own context.

To Reproduce

1. Create a composite action with a post step (like caching) that uses an input
2. Create a composite action that calls the action created in 1
3. Run the action created in 2 in a worflow

Expected behavior
The nested action post step can use the input of it's context.

Runner Version and Platform

Version of your runner? Latest hosted

OS of the machine running the runner? All

What's not working?

Interpolation doesn't work since the context is wrong

See also #2009