Move to MyST as recommonmark and CommonMark are not supported

[Mab879]

Description:

Move the docs to use MyST.

Rationale:

Closes #9076

[github-actions]

Start a new ephemeral environment with changes proposed in this pull request:

Fedora Environment

Oracle Linux 8 Environment

[ggbecker]

We need to update the CMakefiles to reflect this change as they rely on recommonmark for various things. For example:

content/CMakeLists.txt

Line 239 in 5ff88a9

message(STATUS "python recommonmark module (optional): ${PY_RECOMMONMARK}")

but there's more, search for recommonmark and PY_RECOMMONMARK.

The documentation will all require some updates in the dependencies section for the documentation build part.

[Mab879]

I have updated the CMake files and a few other items; there should be no doc changes needed since we instruct to install from docs/requirements.txt.

[codeclimate]

Code Climate has analyzed commit d08a413 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 40.6% (0.0% change).

View more on Code Climate.