Fix CI tests + rename tests

- Fixed CI tests for AArch64 and old x86.
- Rename `simd-umulhi.clif` to `umulhi.clif`.
- Rename `simd-umulhi-aarch64.clif` to `simd-umulhi.clif`.

Copyright (c) 2021, Arm Limited.

cranelift/codegen/meta/src/shared/instructions.rs

@@ -2454,8 +2454,7 @@ pub(crate) fn define(
         Unsigned integer multiplication, producing the high half of a
         double-length result.
 
-        Polymorphic over all scalar integer types, but does not support vector
-        types.
+        Polymorphic over all integer types (vector and scalar).
         "#,
             &formats.binary,
         )