contrib: aom: Backport patches to improve the SVE detection

This backports
https://aomedia.googlesource.com/aom/+/5ccdc66ab6eb8eb300eda854fab4ff250b2c2f92
and
https://aomedia.googlesource.com/aom/+/fb21617c1f3ef49795597e006b68adfba6e54be0.

This makes libaom test compiling a more nontrivial function,
which according to AAPCS requires backing up and restoring SVE
registers.

On current versions of Clang when targeting Windows, compiling such
a function errors out. This added test makes libaom not try to
compile the SVE codepaths for this target.

See https://github.com/llvm/llvm-project/issues/80009 for reference
on toolchain support for SVE functions on Windows on aarch64.