[FEATURE] Enable File Store for publishable actions

**Is your feature request related to a problem? Please describe.**
When I define a reusable action that uses File store, I face an error that `$.files` is undefined

**Describe the solution you'd like**
Enable File Store for publishable actions

**Do you have a workaround?**
No

**Additional context**
Raised by a user here: https://pipedream-users.slack.com/archives/CPTJYRY5A/p1702474373450939

No files or tests are named in the issue. Start by locating the publishable-action runtime and the existing File Store implementation, then trace how $.files is exposed to reusable actions; done means a publishable action can use File Store without $.files being undefined, with coverage for that case.

Written by the indexing model from the issue text.