Instead of having a test for i32 XLen and i64 XLen, use sed to
replace iXLen with i32/i64 before running llc.
This change updates tests for intrinsics that operate exclusively
on mask values. It removes over 4000 lines worth of test content.
More merging will come in future changes.
I would have just committed this, but I didn't want to block the patch to "experimental" from the command lines. I'll rebase after that.