maint(Clang-Tidy): readability-const-return (#3254)

* Enable clang-tidy readability-const-return

* PyTest functional

* Fix regression

* Fix actual regression

* Remove one more NOLINT

* Update comment

.clang-tidy

@@ -31,9 +31,10 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-avoid-const-params-in-decls,
+readability-const-return-type,
 readability-container-size-empty,
-readability-else-after-return,
 readability-delete-null-pointer,
+readability-else-after-return,
 readability-implicit-bool-conversion,
 readability-make-member-function-const,
 readability-misplaced-array-index,