Allow naming classes via their constructors

[supersaiyansubtlety]

Currently IdentifierPanel doesn't allow renaming a class when the caret is in a constructor.

Allowing this should be possible using EntryReference::getNameableEntry.

[supersaiyansubtlety]

looks like this was already intended to work
IdentifierPanel::getRename already got constructors' parent classes, but IdentifierPanel.TableHelper::addRenameTextField checked isRenamable on the entry, not the reference or its nameable entry