postgresql12-12.10-8.29.1

- bsc#1195680: Upgrade to 12.10:
  * https://www.postgresql.org/docs/12/release-12-10.html
  * Reindexing might be needed after applying this upgrade, so
    please read the release notes carefully.
- boo#1190740: Add constraints file with 12GB of memory for s390x
  as a workaround

- Add a llvmjit-devel subpackage to pull in the right versions
  of clang and llvm for building extensions.
- Fix some mistakes in the interdependencies between the
  implementation packages and their noarch counterpart.
- Update the BuildIgnore section.