Side buttons rework

[kirderf1]

Related to #4841 and #4988.

Reworks SideButtonsScreen to not use ModuleScreen, and does some minor additional cleanup.

• The class no longer uses any inheritance to function. Because it no longer extends AbstractContainerScreen or Screen, it will no longer be treated as a screen by other mods. For example, the side buttons will no longer have an InitScreenEvent posted for it. THIS FIXES Inventory Locks show up twice in Tinkers' Construct GUI kirderf1/InventoryFree#9.
• The side buttons widget implements Widget and GuiEventListener but is not added to the parent screen as a screen widget. Instead, render and mouse input functions are called by the parent class directly.
• The parent class no longer has its size (as defined by leftPos and imageWidth etc) expanded to include the the side buttons that normally happens in MultiModuleScreen.updateSubmodule(). With how MultiModuleScreen.render() works, this will not affect any render functions. The size of the widget is still accounted for jei and when dropping items from the screen.
• The side buttons widget now get recreated during the screen.init() call, instead of created in the constructor. This is more inline with how vanilla widgets are handled, and allows us to make the position immutable (which has not been done at this time).
• To remove somenot strictly neccessary instanceof checks and casts in TinkerStationButtonsWidget, SideButtonsWidgetwas made generic for the button type.
• TinkerStationButtonsWidget.selected was replaced by instead checking TinkerStationScreen.currentLayout. Doing so removed any need to copy over data when the widget was recreated during a window resize.

[KnightMiner]

Just a couple of minor things until I have a chance to test this in game.