Finalize sets the release body after the stable tag, the
api/apps/v1alpha1 tag and the release-X.Y fast-forward already exist,
so a body GitHub refuses fails the step with the release still a
draft, and the image retag and chart publish behind it never run.
GitHub's web UI cut the v1.7.0-rc.2 changelog at about 125000
characters, and the v1.7.0 changelog is 259,026.

A release can now carry a short hand-written docs/releasenotes/<tag>.md
that becomes its body, while the changelog stays the full record. Both
finalize and update-releasenotes take the release notes when they have
content and the changelog otherwise, and hold the body to 100000
bytes. Bytes are never fewer than characters, and the margin makes
GitHub's exact limit, and its answer to an oversized body, irrelevant.
Over the limit, finalize publishes a one-line link to the changelog on
the tag instead, and the sync leaves the published body alone: the
tags.yaml backstop brings a changelog to main without its release
notes, and the sync would otherwise replace them.

A release without release notes whose changelog is under the limit
still gets its changelog byte for byte.

Assisted-by: LLM
Signed-off-by: Myasnikov Daniil <[email protected]>
(cherry picked from commit b502a92)