mv pipeline-code from refs/meta/ci:branch.cfg into default-branch

[ccwienk]

Move most contents from refs/meta/ci branch.cfg into default branch. Note that there is a corresponding change that should be done alongside of merging this pull-request (cannot be done via GitHub Pull-Request).

[gardener-robot-ci-3]

This PR proposes changes that would break the pipeline definition:

<invalid YAML>: found undefined alias 'ti_docker_images'
  in "<unicode string>", line 80, column 13:
            <<: *ti_docker_images
                ^

[gardener-robot-ci-3]

This PR proposes changes that would break the pipeline definition:

<invalid YAML>: found undefined alias 'ti_docker_images'
  in "<unicode string>", line 80, column 13:
            <<: *ti_docker_images
                ^

[gardener-robot-ci-3]

This PR proposes changes that would break the pipeline definition:

test-infra-refactor-pipeline-definition: Traceback (most recent call last):
  File "/usr/lib/python3.11/site-packages/concourse/replicator.py", line 141, in render
    definition_descriptor = self._render(definition_descriptor)
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/concourse/replicator.py", line 185, in _render
    'definition': factory.create_pipeline_definition(),
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/concourse/factory.py", line 88, in create_pipeline_definition
    self._apply_traits(variant)
  File "/usr/lib/python3.11/site-packages/concourse/factory.py", line 172, in _apply_traits
    for step in transformer.inject_steps():
  File "/usr/lib/python3.11/site-packages/concourse/model/traits/publish.py", line 475, in inject_steps
    for img in self.trait.dockerimages():
  File "/usr/lib/python3.11/site-packages/concourse/model/traits/publish.py", line 347, in dockerimages
    image_dict = self.raw['dockerimages']
                 ~~~~~~~~^^^^^^^^^^^^^^^^
KeyError: 'dockerimages'

[gardener-robot-ci-3]

The pipeline-definition has been fixed.

[ccwienk]

The pipeline-definition has been fixed.

thank you, @gardener-robot-ci-3

[ccwienk]

this is the remaining branch.cfg we should use after merging this pull-request:

cfgs:
  default:
    branches: ['master']

  release-branches:
    branches: ['rel-.*', 'hotfix-.*']
    inherit:
      test-infra:
        jobs:
          release:
            traits:
              version:
                preprocess: 'finalize'
              release:
                nextversion: 'bump_patch'

[ccwienk]

@dguendisch @hendrikKahl : after merging this pull-request (and updating refs/meta/ci branch.cfg), I will create a second pull-request proposing change from GCR -> Artifact-Registry.
I think it should be easier to do those changes in two separate attempts.

[hendrikKahl]

/lgtm

[hendrikKahl]

4cc7ef4 updates the branch.cfg.