Stop using BREAK & CONTINUE in compiler

Switching them to `Break(())` and `Continue(())` instead.

libs-api would like to remove these constants, so stop using them in compiler to make the removal PR later smaller.

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1428,7 +1428,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
                 }
 
                 fn visit_region(&mut self, _: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
-                    ControlFlow::BREAK
+                    ControlFlow::Break(())
                 }
 
                 fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {