[X86][AVX] Added (V)MOVDDUP / (V)MOVSLDUP / (V)MOVSHDUP memory folding + tests.

Minor tweak now that D7042 is complete, we can enable stack folding for (V)MOVDDUP and do proper testing.

Added missing AVX ymm folding patterns and fixed alignment for AVX VMOVSLDUP / VMOVSHDUP.

llvm-svn: 226873