[Do not merge] Msvc discover toolchain

[shumpohl]

Fix #5 ?

I'm not shure if this works correctly in all cases.

[stefanseefeld]

I just had a look into your patch. The reason it fails one of the CI builds is that you changed the ordering of the found toolchains using a simple lexicographical comparison. So it happens that, while versions above "10" are all correctly ordered, versions "9.x" end up with higher priority and so is chosen for the test runs.
For some reason that version doesn't work with the tests. (We could arguably remove those versions as "too old", but at the same time this simply highlights the fact that your ordering is wrong. (That was one of the reasons why I preferred explicitly listing the known versions in the registry discovery.)

I may look into ways to rewrite the patch, but feel free to follow up yourself.