toolchain resolution may be wrong when python_version does not include a patch version

[aignas]

Whilst writing code for #2657 I noticed that the toolchain matching is acting weirdly when using X.Y format in the python_version field. I noticed that when I write 3.12, the first toolchain gets matched instead of the entry in MINOR_MAPPING.

The fix would be to change the ordering in the toolchain repo to first list the versions in the MINOR_MAPPING before listing the rest of the toolchains.