CI: Add pre-commit hook to use modern testing asserts (#7126)

* Add test to ensure modern testing syntax is used

* auto-fixes for testing formats

* remove usage of depreceated assertDictContainsSubset

.pre-commit-config.yaml

@@ -84,3 +84,7 @@ repos:
 #    rev: 3.0.0
 #    hooks:
 #    -   id: shellcheck
+-   repo: https://github.com/isidentical/teyit
+    rev: 0.4.3
+    hooks:
+    -   id: teyit