Rollup merge of #154248 - lms0806:issue_154034, r=TaKO8Ki

resolve :  mark repr_simd as internal

I changed ```repr_simd``` to ```internal``` and changed the position to ```feature-group-start: internal feature gates```.

close rust-lang/rust#154034

compiler/rustc_feature/src/unstable.rs

@@ -303,6 +303,8 @@ pub fn internal(&self, feature: Symbol) -> bool {
     (internal, panic_runtime, "1.10.0", Some(32837)),
     /// Allows using pattern types.
     (internal, pattern_types, "1.79.0", Some(123646)),
+    /// Allows `repr(simd)` and importing the various simd intrinsics.
+    (internal, repr_simd, "1.4.0", Some(27731)),
     /// Allows using compiler's own crates.
     (unstable, rustc_private, "1.0.0", Some(27812)),
     /// Allows using internal rustdoc features like `doc(keyword)`.
@@ -657,8 +659,6 @@ pub fn internal(&self, feature: Symbol) -> bool {
     (incomplete, ref_pat_eat_one_layer_2024_structural, "1.81.0", Some(123076)),
     /// Allows using the `#[register_tool]` attribute.
     (unstable, register_tool, "1.41.0", Some(66079)),
-    /// Allows `repr(simd)` and importing the various simd intrinsics.
-    (unstable, repr_simd, "1.4.0", Some(27731)),
     /// Allows bounding the return type of AFIT/RPITIT.
     (unstable, return_type_notation, "1.70.0", Some(109417)),
     /// Target features on riscv.

library/alloctests/benches/lib.rs

@@ -1,5 +1,6 @@
 // This is marked as `test = true` and hence picked up by `./x miri`, but that would be too slow.
 #![cfg(not(miri))]
+#![allow(internal_features)]
 #![feature(iter_next_chunk)]
 #![feature(repr_simd)]
 #![feature(slice_partition_dedup)]