Rollup merge of #136191 - klensy:const_a, r=compiler-errors

compiler: replace few consts arrays with statics to remove const dupes

Locally on `x86_64-pc-windows-msvc` -100kb for `rustc_driver.dll`

compiler/rustc_feature/src/unstable.rs

@@ -104,7 +104,7 @@ macro_rules! declare_features {
     )+) => {
         /// Unstable language features that are being implemented or being
         /// considered for acceptance (stabilization) or removal.
-        pub const UNSTABLE_LANG_FEATURES: &[Feature] = &[
+        pub static UNSTABLE_LANG_FEATURES: &[Feature] = &[
             $(Feature {
                 name: sym::$feature,
                 since: $ver,