Add fancier CI badges showing number of tests and/or test coverage

[ScottTodd]

We could add badges for each test suite showing the number of tests, like those at https://github.com/onnx/onnx-mlir?tab=readme-ov-file#onnx-mlir

These projects could help:

• https://github.com/marketplace/actions/ci-badges (hooks up to coverage reports, generates badges, uploads to gists, provides URLs that can be used with badge endpoints to render SVGs)
• https://pypi.org/project/pytest-local-badge/ (generates local svgs)

I'd see how other projects use pytest-local-badge. Maybe we can push the svg files to a branch automatically.

[ScottTodd]

Not finding too many resources for CMake/CTest badges. Here are a few though, focused on CDash (dashboards):

• https://cmake.org/cmake/help/latest/guide/tutorial/Adding%20Support%20for%20a%20Testing%20Dashboard.html
• https://cmake.org/cmake/help/book/mastering-cmake/chapter/CDash.html
• https://github.com/jcfr/CBadge