Feature Request: Support for multiple `pre_build` & `post_build` run scripts

Problem

At present pre_build & post_build run scripts take a single script each. This means If I want to run multiple post_build run scripts then I need to combine them in a single script and pass that to post_build argument, this works fine but this limits us from providing Inputs & Outputs to these Individual run scripts.

What I am trying to do

We have a script to copy some files to the generated app bundle, running that each time is costly hence I was thinking to add it as a separate run script and specify Inputs/Outputs.

Feature Request

Instead of a single script, accept an array of scripts in pre_build & post_build and also provide an option to specify scripts Inputs & Outputs.

P.S This feature also depends on issue/feature raised here - https://github.com/MobileNativeFoundation/rules_xcodeproj/issues/2108

Start by reviewing the current handling of pre_build and post_build scripts, then read issue 2108 because this request depends on it. Done means both options accept multiple scripts and each script can declare its own inputs and outputs.