MDL-38520 JavaScript: Migrate moodle-core-formchangechecker to use Shifter
MDL-38516 JavaScript: Migrate moodle-block_navigation-navigation to use Shifter
MDL-38741 formslib: don't complain about frozen elements
MDL-38741 formslib: actually track hidden element freezes
MDL-38741 qtype_truefalse: freeze penalty element