Rollup merge of #106917 - compiler-errors:const-closure-foreign, r=tmiasko

Encode const mir for closures if they're const

Fixes #106913

tests/ui/consts/auxiliary/closure-in-foreign-crate.rs

@@ -0,0 +1,8 @@
+#![crate_type = "lib"]
+#![feature(const_closures, const_trait_impl)]
+#![allow(incomplete_features)]
+
+pub const fn test() {
+    let cl = const || {};
+    cl();
+}

tests/ui/consts/closure-in-foreign-crate.rs

@@ -0,0 +1,8 @@
+// aux-build:closure-in-foreign-crate.rs
+// build-pass
+
+extern crate closure_in_foreign_crate;
+
+const _: () = closure_in_foreign_crate::test();
+
+fn main() {}