Add basic automated tests

[bjoernQ]

This just adds some very basic automated tests to be run locally. It's basically an automated version of smoketest.bat which I use to verify things still work - but the manual process takes > 1h so this should help a little bit.

The test runner could use some improvements but I now have a first version which is apparently useful and worth to evaluate. The current set of tests only test the non-async code and basically adaptions of the existing examples - I will add more tests when I get to that

Long-term goal is to unify the tests here and the HIL testing we will have in esp-hal one day. Maybe even running the tests during CI - but for now, this is better than having nothing

In any way this shouldn't annoy most users - the only file this messes with is the examples section in Cargo.toml which shouldn't be a big problem. Last not least I will maintain the tests myself so no problem for future contributors

[MabezDev]

LGTM, maybe in the future we can replace the .bat with an xtask command so unix folks can run it too, but given that you're doing most of the testing you're the priority at the moment :D.

[bjoernQ]

Good idea to use an xtask - was thinking about a justfile otherwise but the .bat was the fasted thing. Thanks