Remove Jetpack release automation in favour of local scripts

Delete the workflows and helper scripts that implemented the old
Jetpack-driven release pipeline so they do not fight the new manual
`make pre-build` / `make build` / `make publish` flow:

- .github/workflows/autotagger.yml (tag pushes from CHANGELOG.md).
- .github/workflows/autorelease.yml (GitHub release from a tag push).
- .github/workflows/wp-svn-autopublish.yml (WordPress.org SVN publish).
- .github/workflows/changelogger.yml (per-PR changelog entry check).
- .github/files/autorelease.sh and wp-svn-autopublish.sh helpers.

Add `make publish` via scripts/publish.sh: creates a GitHub release
from readme.txt + build/wp-super-cache.zip, then optionally publishes
to WordPress.org SVN (shallow checkout under build/svn, rsync into
trunk, svn cp to tags/<version>).

Author: donnchawp