ci: add reusable workflows

[umarcor]

This PR adds 11 reusable workflows, based on the jobs used in repos from this organisation, EDA², VHDL, and others.

The expected order is:

• Params.yml
• UnitTesting.yml
• CoverageCollection.yml
• StaticTypeCheck.yml
• Release.yml
• Package.yml
• PublishOnPyPI.yml
• VerifyDocs.yml
• BuildTheDocs.yml
• PublishToGitHubPages.yml
• ArtifactCleanUp

Moreover, an example workflow named ExamplePipeline.yml is provided, for tool developers to copy it into their repos. The only required modification should be setting the name input of job Params.

IMPORTANT: reusable workflows must be used through an absolute name and specifying a version (see actions/runner#1493). Therefore, this PR will be kept as a draft, because s/@dev/@main/ is required in ExamplePipeline.yml before merging.

[umarcor]

@Paebbels, as discussed in the meeting, I did several enhancements to this PR:

• rename 'pyver' to 'python_version'
• add option 'requirements' to Package, PublishOnPyPI, StaticTypeCheck, UnitTesting and CoverageCollection.
• update StaticTypeCheck to make the html report optional and to accept mypy args (instead of just the package name).
• do not delete the wheel/dist artifact in job PublishOnPyPI.
• generate matrix/list of jobs for UnitTesting dynamically (in job Params). allow overriding it by providing a list of space separated versions.

Furthermore, I updated the example pipeline, to show all the required and optional inputs.

This is currently tested in three repos:

• https://github.com/edaa-org/pySVModel/actions (neither StaticTypeCheck nor VerifyDocs, yet)
• https://github.com/edaa-org/pyEDAA.ProjectModel/actions (the list of python versions is overriden)
• https://github.com/VHDL/pyVHDLModel/actions (a custom VerifyDocs job is used)

[umarcor]

Since the ArtifactCleanUp job now has more than one step, I created a reusable workflow. I tested it in pyEDAA.ProjectModel, successfully.

I changed s/@dev/@main/ in ExamplePipeline.yml. So, I think this is ready to merge.