Rollup merge of #107555 - edward-shen:edward-shen/dup-trait-suggestion, r=compiler-errors

Modify existing bounds if they exist

Fixes #107335.

This implementation is kinda gross but I don't really see a better way to do it.

This primarily does two things: Modifies `suggest_constraining_type_param` to accept a new parameter that indicates a span to be replaced instead of added, if presented, and limit the additive suggestions to either suggest a new bound on an existing bound (see newly added unit test) or add the generics argument if a generics argument wasn't found.

The former change is required to retain the capability to add an entirely new bounds if it was entirely omitted.

r? ``@compiler-errors``

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -679,6 +679,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         &param_name,
                         &constraint,
                         Some(trait_pred.def_id()),
+                        None,
                     ) {
                         return;
                     }
@@ -1087,6 +1088,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     param.name.as_str(),
                     "Clone",
                     Some(clone_trait),
+                    None,
                 );
             }
             err.span_suggestion_verbose(