[WIP] Add scripts for building RPMs and creating release draft

[shinyaaa]

Summary

• Build RPMs when tags are pushed and attach them to the draft release.
• This PR is in progress.
  • When PostgreSQL 17 is released, we need to add ‘17’ to PG_VERSION and check that it works properly.

How to test this PR

1. Fork pg_bulkload to your repository and execute below commands.

git clone https://github.com/<username>/pg_bulkload.git
cd pg_bulkload
git remote add remote https://github.com/ossc-db/pg_bulkload
git fetch remote pull/164/head:add-auto-rpm-build
git switch add-auto-rpm-build
git commit -m test --allow-empty
git tag VERSION3_1_21 -f
git push origin VERSION3_1_21 -f

2. Access https://github.com/username/pg_bulkload/actions
3. Sometimes the script hangs. When this happens, press ‘Cancel workflow’ and re-run with ‘Re-run failed jobs’.
4. Check release draft at https://github.com/username/pg_bulkload/releases