1.7.10-1.16.5: Add option to preload models

Option in the config to enable preloading models.
This will increase startup time, but:

• Lowers lag spikes while opening the landofsignals creative tabs for the first time
• Lowers lag spikes while loading chunks with different signals
• Crashes game sooner with broken contentpacks, which will help creators
• Can be used later on for dynamic item scaling (different feature - will be tried afterwards)

TODOs

• Models can be loaded on startup
• Merged into develop
• Merged into umc-2.0 branch