[POC] Github Actions support for OSX platform

[uilianries]

Related to #17028

Add support for Conan client tests, running on OSX, using Github Actions.

/cc @czoido

• Refer to the issue that supports this Pull Request.
• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one.

[uilianries]

@perseoGI At this point all dependencies are installed, according to Conansible. For some reason, CMake can not find the compiler, but the same looks configured already.

Still there is window for improvement, like using cache for installed dependencies.