Added default source revision file name to common.py.
Modified the integration_into_manifest function to set the
corresponding subproject hash in the SRCREV.conf file if the
repository is not found in the default.xml file. The
merge_into_manifest function now works even if the names of
the master branches in the manifest and in the project
repository are different.

BCS 746-000016

Fix pylint errors introduced with new pylint version:
* unspecified-encoding: explicitly set encoding when opening a file
* assigning-non-slot: use "set_reference()" function instead of assigning
  a value to the "reference" attribute
* unused-variable: remove "e" variable on exceptions when not referenced

The jobs in the deploy stage have to be triggered manually in GitLab.
There is one deploy job for each project which uses the gitlab-ci
scripts as a submodule, so that the deployment can be performed step by
step.

If executed within MR context, an integration MR is created and left
open. The user can extend this integration MR, e.g. if CI scripts have
been renamed, changed command line arguments or other changes requiring
updates of the correspronding .gitlab-ci.yml file. Subsequent runs of
this job will re-create the integration branch, so manual changes are
lost in this case.

If executed on the master branch (i.e. after the source MR has been
merged), the job does exactly the same, plus the integration MR will be
automatically merged. If this fails, the job will fail as well.

We still had cases where a merge request was rebased multiple times after an
initial (actually required) rebase:

https://gitlab.com/garz-fricke/yocto/infrastructure/ci-test/minimal-bar/-/jobs/1345964713

I assume that GitLab simply does not update the MR that fast and so we attempt
to do a rebase, while the MR still reports it is merge-ready.

Adding a wait loop now where the MR's sha is compared to the one of the new
commit in order to make sure that the MR has been updated before we attempt
another rebase.

We had some cases where the merge job added rebases of a commit where rebasing
was not necessary at all, e.g.:
https://gitlab.com/garz-fricke/yocto/layers/meta-guf-machine/-/jobs/1270293595

This is obviously a known issue in GitLab concerning the HTTP return value of
the merge endpoint:
https://gitlab.com/gitlab-org/gitlab/-/issues/196962

Suggested workaround is to manually check merge_status and wait until it is
ready before attempting to merge the MR.

The canceling was required when a reintegration was necessary before merging. The instant merge afterwards deleted the integration branch, so the pipeline on the branch would fail, because repo cannot checkout the code anymore. With minimal-manifest!126 we started checking out code using refs/pipelines/<id> instead of explicit branch/tag names. This ref still exists when the branch is already deleted (see https://docs.gitlab.com/ce/ci/pipelines/#ref-specs-for-runners), so the pipeline canceling is not necessary anymore.

* Before, only the latest commit was included
* Use merge request ID instead of branch name and commit in the argument list

* Add retrigger_mr_pipeline_py script
* Move get_merge_request() function to separate file and make it return all
  available pipelines instead of just one
* Add helper script for parsing projects from manifest file