ci: code size comment from stored master snapshots, ESP included (#4055)

- Size pinned boards' examples (ESP-IDF and -DMA variants included) with membrowse 1.2.12 and store per-board snapshots as artifacts.
- Compare a PR against the stored master snapshots and post one sticky comment: each changed TinyUSB file with its min to max Flash/RAM delta, plus what was not compared; the full report goes to the job summary and an artifact.
- Retire the Membrowse PR comment.
- Add tools/code_size.py report/diff for local runs, and the code-size skill.