[llvm] [CodeGen] Add MO_LaneMask type and a new COPY_LANEMASK instruction (PR #151944)

[Jay Foad via llvm-commits]

================
@@ -807,6 +807,23 @@ For an int eq predicate ``ICMP_EQ``, the syntax is:
 
    %2:gpr(s32) = G_ICMP intpred(eq), %0, %1
 
+LaneMask Operands
+^^^^^^^^^^^^^^^^^^
----------------
jayfoad wrote:

```suggestion
^^^^^^^^^^^^^^^^^
```

https://github.com/llvm/llvm-project/pull/151944