QuestHelperPlugin file refactor (#1294)

* Reorganize existing file structure

* Add QuestOverlayManager

This takes over the Overlay management from QuestHelperPlugin.

* Add QuestBankManager

This is intended to handle bank behaviour for the QuestHelperPlugin.

* Restructure RuneliteObject usage

Merges Cheerer with the overall RuneliteObjectMananger.

* Extract QuestHelper from QuestHelperPlugin

This manager handles starting up and closing down helpers.

* Swap menu entry swapping to use onClick

* Add javadocs to QuestManager

* Document + refactor QuestNameToHelper

* Fix sidebar panel highlighting on start

* Remove redundant check of questBankTab being null.

* Remove setVisible from RuneliteObjectManager