[3.0] CI: add Windows ARM64 build targets/fix Qt5 with recent mingw-w64

It's the same target as for VLC 4.

• It's using UCRT (rather than MSVCRT).
• It is built with LLVM 15.
• It is targeting Windows 10 1809 = Redstone 5.
• extra checks (-x) are not enabled as the code has not been cleaned on 3.0 as in 4.0.

I expect DVD navigation to be broken until !2400 (merged) is merged and backported.