Rollup merge of #122107 - Urgau:non_local_def-allow, r=WaffleLapkin

Temporarily make allow-by-default the `non_local_definitions` lint

T-lang [decided in their triage meeting](https://hackmd.io/U-CKiZx_RKiaANAPXtWf7g#non_local_definitions-common-issues-impl-for-ampLocal-FromltLocalgt-for-Global-%E2%80%A6-rust121621) to try to use a [better logic](#121621 (comment)) for detecting non-local `impl` definitions given the [numerous reports](#121621) we got.

Until that is done and also because the beta cut is next week, switch the lint to allow-by-default until it's implemented.

r? `@WaffleLapkin`

Author: matthiaskrgr

compiler/rustc_lint/src/non_local_def.rs

@@ -14,6 +14,7 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
+    /// #![warn(non_local_definitions)]
     /// trait MyTrait {}
     /// struct MyStruct;
     ///
@@ -36,7 +37,7 @@ declare_lint! {
     /// All nested bodies (functions, enum discriminant, array length, consts) (expect for
     /// `const _: Ty = { ... }` in top-level module, which is still undecided) are checked.
     pub NON_LOCAL_DEFINITIONS,
-    Warn,
+    Allow,
     "checks for non-local definitions",
     report_in_external_macro
 }

tests/ui/lint/non_local_definitions.rs

@@ -4,6 +4,7 @@
 //@ rustc-env:CARGO=/usr/bin/cargo
 
 #![feature(inline_const)]
+#![warn(non_local_definitions)]
 
 extern crate non_local_macro;