Improve lang resource pack injection point (closes #532)

Previously we injected it as a regular builtin resource pack (like the
Programmer Art pack) and hid it on the resource pack screen but this is bad for
several reasons. The most significant one being that it can be re-ordered and
makes the resource pack list ordering weird if you don't know that there is an
invisible pack there.
It also unnecessarily messes with other mods which make certain assumptions
about configurable resource packs (e.g. EBE, though in that case, it merely
triggers an existing bug in EBE).

We now instead inject it into the final resource pack list which gets
constructed from the configured packs, but never as a configurable pack itself.

src/main/resources/mixins.core.replaymod.json

@@ -8,8 +8,7 @@
     //#if MC>=11400
     "AbstractButtonWidgetAccessor",
     "MixinGameRenderer",
-    "Mixin_HideDynamicResourcePacks",
-    "Mixin_RegisterDynamicResourcePacks",
+    "Mixin_InjectDynamicResourcePacks",
     //#endif
     //#if MC>=11400
     "MixinMouse",