Getting Rid of Experimental Mode

[andybak]

Here's the branch: https://github.com/icosa-gallery/open-brush/tree/merge-experimental

Provisional Plan

Get Rid of the separate build

• Remove compile directives and rely entirely on Config.IsExperimental
• Make Config.IsExperimental derive from a PlayerPref
• Add a UI for the PlayerPref

At this point (in theory) we should have a single build that allows you to switch between normal and experimental mode by ticking a checkbox in the UI and restarting. Some features might work without a restart depending on code flow.

Begin to remove separate experimental mode entirely

• Move the brushes we want to keep to the main manifest. Initially rely on brush tags to hide them by default
• Move Experimental panel buttons to Labs panel (and maybe move some Labs items to Advanced Tools)
• Fix Toolkit/SDK and three.js loader to support the previously experimental brushes that we decide to keep
• Remove the "experimental" tag so those brushes appear by default

Provisional brush list is here: https://docs.google.com/spreadsheets/d/12fHPnMNhpGGdR1mzFeCjXbg1Nv1PO1LZGcHwgp3S1Og/edit#gid=1183826559 (on the third tab - the one labelled "Experimental Brush Status")

Notes from my investigation into places in the code that rely on Experimental Mode is here: https://docs.openbrush.app/developer-notes/differences-between-standard-and-experimental-mode