This reimplements the CI deployment functions, and makes them a bit more
robust.  Concretely:

- Introduce a generic "deployment tag" option that can be used to
  override the tag to use for specific images. By default, it is the
  current "branch-commitID[0:8]" tag name (requires the change from
  function ImageTagToUse() to CreateTag(), impacting also pull/push
  image functions)
- Avoid sed for image names, and use an .env file that docker-compose
  picks up automatically; the deployment analyzes a potentially existing
  .env file and updates instead of simply overriding. For instance, some
  pipelines might use -asan images for the gNB and "normal" (non-asan)
  images for UE, and a simple overwriting might make the -asan image
  name tag disappear for the gNB, resulting in deployment failures).
  Finally, undeployment removes the .env file, so that there are no
  modifications in the repository after undeployment.
- Redo the previous behavior of autodetecting asan, and use that (the
  current function always uses asan, no matter what)
- Remove deployKind/displayedNewTags globals, as they are not necessary
- Make the usedImage output in HTML slimmer
- On undeployment, print service names next to undeploy analysis, and
  return success/failure.
- Make the functions generally less verbose and easier to read

Note that as of and only in this commit, deployment does not work, as
all the YAML files have not been updated to work with this updated
version.  The next commit adds tests for the new deployment, and updates
one YAML file (also being used in the tests). The follow-up commit then
modifies all YAML files.