Prepare gcmole.cc for the next update:
- Print possible GC locations when discovering stale/dead variables
- Make error messages less confusing for the modern V8 engineer
- Prepare gcmole to read suspects.allowlist instead of .whitelist
- Use more readable variable names
- Only log non-found types with --verbose
- Change the currently unusued gccauses format in gcmole.py and
  support loading it back in gcmole.cc
- Implemented first basic gc call-chain printing (disabled by default)

GCmole packaging:
- Add debug mode to bootstrap.sh build script
- Update gcmole.py run instructions in bootstrap.sh and package.sh

Bug: v8:10009
Change-Id: I369d48baa2980455d2e8f57e7a803d0384fe83f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3480095Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79357}