Add support for CI in PRs that target feat/... branches

[wulfraem]

Description of change

Add support for CI in PRs that target feat/... branches, and removes CI triggers for epic/... branches (currently unused).

The audit workflow has been enabled for support/... targeting PRs as well. Summary of changes:

workflow	change
audit	+ feat/** + support/**
build-and-test-grpc	* epic/** -> feat/**
build-and-test	* epic/** -> feat/**
clippy	* epic/** -> feat/**
format	* epic/** -> feat/**

Type of change

Add an x to the boxes that are relevant to your changes.

• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix
• CI

How the change has been tested

Checked format, etc. locally, PR's CI should be triggered when openening this PR.

Change checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes