Changes

debian-bookworm-titan{,-master}: new containers

Add new containers based on debian-bookworm. Make some improvements
over the bullseye containers while at it:
* Remove sed for cversion.h, as the #error it is trying to replace is a
  warning now so it is a no-op, and we use our own eclipse-titan package
  instead of debian's package.
* Make apt commands consistent
* Move commands around to make better use of the cache
* Clone osmo-python-tests from gerrit instead of gitea and invalidate
  cache when master changes
* Tweak comments

Related: OS#6057
Change-Id: I4415fcde6518bd26d1e2cb5785ddaf84ac2116b3

ttcn3: use debian-bookworm-titan

Related: OS#6057
Change-Id: I2017dd3888670c475b96e692d911a433484f3df9