meson: Test support for aarch64 extensions with gas-preprocessor (MS armasm64) too

This allows building the more modern aarch64 extension code (dotprod, i8mm, sve) with MSVC/armasm64 too.

See https://github.com/mesonbuild/meson/issues/12396 and https://github.com/mesonbuild/meson/issues/12395 for discussions about the Meson challenges around doing the configure time tests for these features.