[rocm-libraries] ROCm/rocm-libraries#4943 (commit ea40212)

[CK] Updating CI skip logic (#4943)

## Motivation

The CI skip logic has two issues that prevented it from working
correctly:

1. **Incorrect file patterns**: After migrating from standalone repo to
`rocm-libraries`, file paths now include the
`projects/composablekernel/` prefix (e.g.,
`projects/composablekernel/docs/README.md`). The skip patterns were
still checking for paths starting with `docs/`, which never matched.

2. **Incomplete build type support**: Jenkins multibranch pipelines
provide different environment variables for PR builds (`$CHANGE_TARGET`,
`$CHANGE_ID`) vs branch builds (`$BRANCH_NAME`). The previous logic only
compared `HEAD~1..HEAD` for branch builds, which missed changes from
multi-commit pushes and didn't properly handle feature branch builds.

When CI skipped or ran, there was no visibility into which files
triggered the decision, making it difficult to diagnose issues. You can
now see which files triggered the CI run.

## Technical Details

PR builds: Compares all commits against origin/$CHANGE_TARGET.
Feature branch builds: Uses git merge-base to find divergence point from
develop and checks all touched files since then.
Scheduled develop builds are unaffected. These builds are forced to run
from the pipeline parameters.

Example log output for PR Builds:
<img width="647" height="260" alt="image"
src="https://github.com/user-attachments/assets/c8673a81-acb2-4fb2-acbb-1c07b5ab3b69"
/>

Example log output for Branch Builds:
<img width="488" height="287" alt="image"
src="https://github.com/user-attachments/assets/fbb17ba7-eb2c-42a4-b820-b2a8b9e479c4"
/>

## Test Plan

Pre-PR validation (branch builds):

Push commits with only documentation changes → CI should skip. I will
have to verify this after this PR is merged!
Push commits with code changes → CI should run
Push commits that modify then revert code → CI should run (catching
reverts)
Verify debug output clearly shows skip/run decision

Post-PR validation (PR builds):

Create PR with only doc changes → CI should skip. I will have to verify
this after this PR is merged!
Create PR with mixed doc + code changes → CI should run and log which
files triggered it
Verify debug output clearly shows skip/run decision

## Test Result

All branch build checks succeeded.
All PR build checks succeeded.

## Submission Checklist

- [x] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.