[X86] Update some avx512 fast-isel tests to match their real clang IRgen.

Especially of note was the test_mm_mask_set1_epi64 and other set1 tests that were truncating the element to be broadcasted to i8 and broadcasting that instead of a whole 64 bit value.

Some of the others were just correcting mask sizes on parameters due to bugs in the clang test case they were generated from that have now been fixed.

Some were converting i8 to <4 x i1>/<2 x i1> by truncating to i4/i2 and then bitcasting. But the clang codegen is bitcast to <8 x i1>, then extract to <4 x i1>/<2 x i1>. This is likely to incur less trouble from the integer type legalizer in the backend.

llvm-svn: 336045