Integrate gitlab-ci/add-release-suffix and 3 more

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@543a2170

manifest_package: add release suffix

Customer specific manifest projects can now set the RELEASE_SUFFIX
variable, which then gets appended to the deployment folder names.

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@c763c43f

alphaplan_fwr: change variable "release_name_local" to "release_name"

Otherwise it can be assumed that it might be correlated with
outputdir_local, which is not the case.

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@2d8d26a5

package_release: more refactoring

- Make output-dir an argument that can be passed multiple times instead
  of hard-coding two dirs with certain meanings.
- Remove LOCALDIR variable from package.env, because it is not used
  anywhere (only occurence was job class ".uploadsdkftp" which wasn't
  used anywhere either).

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@dc3698c8

package_release: refactoring

Improve readability of package_release.py and its submodule
generate_release_metadata.py.

- Add describing comments throughout the file.
- Remove duplicate code from functions. Simplify them, so that they do
  what their names say (and nothing more).
- Rename variables and function arguments to make their purpose clearer.
- Harmonize variable names with their corresponding command line arguments.
- Add pydoc for functions.
- Add type declarations to function arguments.
- Generate MD5 and metadata files in the source directories so that they
  can be copied along with the rest of the files.