Let LLMs create less noisy and more focused PR descriptions (#94896)
The default template is too noisy when used by LLMs. "what" and "how"
are almost always duplicates. Verification most often includes trivial
commands (e.g. static checking of .js files or running `pnpm build`).
This information isn't relevant to review and can leave the important
bits of a PR description unreviewed.
Oftentimes the "why" is the most important bit for maintainers. The
"what" is most important for end users reading along (or for deriving
docs or changelog entries from the PR).