Use Context Predicates for Mixin Loading

[WaitingIdly]

changes in this PR:

• fix a mixin accessor trying to load Minecraft, which is a client-only class, on the server (generates a warning).
• use Predicate<Context> instead of BooleanSupplier for mixin loaders.
• use Context to check if mods are loaded, replacing all loaded({modid} with c.isModPresent({modid}).
• change isDev() to be part of the predicate.
• change Coremods#isLoaded to just be Context#isModPresent checks directly, and remove now-unused Coremods

[what-the-diff]

PR Summary

• Removal of Certain Core Modifications
  A number of core modifications housed in the file Coremods.java were removed. This includes modifications known as OPENMODS, RANDOM_PATCHES, RENDERLIB, SPONGEFORGE, and SURGE. Simplifying this file can make the code easier to maintain and possibly increase efficiency.

• Added Client-Side Mixin iniclusion
  An entry has been added to the mixins.vanilla.mod.accessors.json file to include UTMinecraftAccessor for client-side mixins. This entry can help improve the game's performance on client side by modifying its behaviors and interactions.