This update for postgresql, postgresql12 fixes the following issues:

Postgresql12 was updated to 12.3 (bsc#1171924).

- https://www.postgresql.org/about/news/2038/
- https://www.postgresql.org/docs/12/release-12-3.html

- Let postgresqlXX conflict with postgresql-noarch < 12.0.1 to get
  a clean and complete cutover to the new packaging schema.

Also changed in the postgresql wrapper package:

- Bump version to 12.0.1, so that the binary packages also have
  a cut-point to conflict with.

- Conflict with versions of the binary packages prior to the
  May 2020 update, because we changed the package layout at that
  point and need a clean cutover.

- Bump package version to 12, but leave default at 10 for
  SLE-15 and SLE-15-SP1.