Rollup merge of #138003 - sayantn:new-amx, r=Amanieu

Add the new `amx` target features and the `movrs` target feature

Adds 5 new `amx` target features included in LLVM20. These are guarded under `x86_amx_intrinsics` (#126622)

 - `amx-avx512`
 - `amx-fp8`
 - `amx-movrs`
 - `amx-tf32`
 - `amx-transpose`

Adds the `movrs` target feature (from #137976).

`@rustbot` label O-x86_64 O-x86_32 T-compiler A-target-feature
r? `@Amanieu`

compiler/rustc_span/src/symbol.rs

@@ -1378,6 +1378,7 @@ symbols! {
         movbe_target_feature,
         move_ref_pattern,
         move_size_limit,
+        movrs_target_feature,
         mul,
         mul_assign,
         mul_with_overflow,