Pages hide the sidebar, boss bars and action bar

• New: while a player has a page open, MC GUI hides the sidebar scoreboard, boss bars and action bar other plugins draw, and puts each back as the server last had it when the page closes, however it closes. Before, they showed over a page whenever another plugin's pack replaced MC GUI's shaders (Dialog Engine's drawn dialogs merged into another pack, for one).
• It works for that player alone, with packets, so it works with TAB, ProtocolLib, PacketEvents and any other plugin that draws them. MC GUI's own action bar messages still show; the tab list, chat, titles and the text under names are never touched.
• All three are on by default. Turn any of them off under views.hide-hud in config.yml (scoreboard, boss-bars, action-bar) to keep it on screen at pages. Read at startup.
• For plugin developers: ViewOptions.hud(HudParts) chooses per view (HudParts.NONE hides nothing, HudParts.ALL.actionBar(false) all but the action bar). The old three-argument ViewOptions constructor still works and uses the config.
• Fixed: Spigot 1.21.11's name table was regenerated.