Custom Machinery Mekanism 1.21.1-1.4.1

• Fix heat element builder resetting custom texture when editing heat gui element.
• Update to latest mekanism version, this change everything related to chemicals.
  • Now "custommachinery:gas", "custommachinery:slurry"... are all unified under "custommachinery:chemical".
  • That goes for machine components, recipe requirements and gui elements.
  • For KubeJS the change is from requireGas, requireSlurry etc... to requireChemical.
• Better parsing of chemicals in KubeJS script, the syntax is now the same as items and fluids : "500x mekanism:steam" will give 500mB of steam gas.