[AArch64-SVE]: Force generating code compatible to streaming mode.

When streaming mode is enabled, lower some operations and disable some code paths;
to force generateing code compatible to streaming mode.
Add streaming-mode flag for new sve-fixed-length testing files:
build_vector.ll
concat.ll
extract-subvector.ll
extract-vector-elt.ll
int-shifts.ll
loads.ll
shuffle.ll
stores.ll

Differential Revision: https://reviews.llvm.org/D135564