Consistently use dominates instead of is_dominated_by

There is a number of APIs that answer dominance queries. Previously they
were named either "dominates" or "is_dominated_by". Consistently use the
"dominates" form.

No functional changes.

compiler/rustc_middle/src/mir/mod.rs

@@ -3049,7 +3049,7 @@ impl Location {
         if self.block == other.block {
             self.statement_index <= other.statement_index
         } else {
-            dominators.is_dominated_by(other.block, self.block)
+            dominators.dominates(self.block, other.block)
         }
     }
 }