Add script and pipeline that automatically bumps gVisor version

[MrBatschner]

What this PR does / why we need it:

Adds a script and a pipeline that checks for new/updated gVisor versions at regular intervals and files a pull request should a new version be found.

Release note:

NONE

[MrBatschner]

This PR proposes changes that would break the pipeline definition:

gardener-extension-runtime-gvisor-dev_automatic-gvisor-bump: Traceback (most recent call last):
  File "/usr/lib/python3.12/site-packages/concourse/replicator.py", line 141, in render
    definition_descriptor = self._render(definition_descriptor)
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/concourse/replicator.py", line 185, in _render
    'definition': factory.create_pipeline_definition(),
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/concourse/factory.py", line 88, in create_pipeline_definition
    self._apply_traits(variant)
  File "/usr/lib/python3.12/site-packages/concourse/factory.py", line 177, in _apply_traits
    transformer.process_pipeline_args(pipeline_def)
  File "/usr/lib/python3.12/site-packages/concourse/model/traits/release.py", line 520, in process_pipeline_args
    raise ValueError(textwrap.dedent(f'''\
ValueError: asset=BuildstepLogAsset(ocm_labels=[{'name': 'gardener.cloud/purposes', 'value': ['lint', 'sast', 'gosec']}, {'name': 'gardener.cloud/comment', 'value': 'We use gosec (linter) for SAST scans, see: https://github.com/securego/gosec.\nEnabled by https://github.com/gardener/gardener-extension-runtime-gvisor/pull/155\n'}], type='build-step-log', name='verify-build-step-log', step_name='verify', artefact_type='application/data', artefact_extra_id={}, purposes=['lint', 'sast', 'gosec'], comment='We use gosec (linter) for SAST scans, see: https://github.com/securego/gosec.\nEnabled by https://github.com/gardener/gardener-extension-runtime-gvisor/pull/155\n', upload_as_github_asset=True, github_asset_name=None)'s step_name refers to an absent build-step. If the step in question is
declared branch-specifically, i.e. via `branch.cfg`, and the current branch is
going to be merged with a branch declaring the pipeline step, this error can be
safely ignored, iff the branch is transient only (not used for release).

This comes from the changes to pipeline_defitinitions in #173, check my comment there.