[ETF] Entity Texture Features

[6.2]

• forge 1.21 & 1.20.6 fixed
• changed gui icon
• added checks to ensure random property suffixes are always valid integers above 0
• fixed crash when rendering entity nameplates and having renderlayer overrides affect entity shadows
• fixed the skin pixel transparency override setting in skin features not affecting all of the pixels correctly
• reworked and improved the nbt property to improve both performance and log printing functionality
  • if your nbt test starts with print_all: the entire entity client-side nbt will be printed with nice formatting
  • if your nbt test starts with print: that specific nbt value will be printed every time it tests, as well as its result
  • (these will go before tests like raw:, exists: or range:, e.g. print_all:exists:false)
• made many minor source code adjustments, no functionality changes, no API changes