Re-implements GAGS config loading and icon generation using IconForge, can basically 1:1 replace any GAGS generate() tasks in DM and can be up to 250x faster per unique config-color combination. Worst case goes from 250ms to 1ms.

Works by outputting the result to a DMI in tmp and assigning it to icon in DM.

This version of GAGS does not support (it will soft fail and just not generate the icon correctly):

• The color_matrix layer type
• The or blending mode
• BYOND Parity on obscure operations with multiple icon_states at the same time (animated sprites, unscoped/stateless icons, mixed-dirs aka overlaying icons with different dir amounts)

A DM implementation can be found in this PR: BeeStation/BeeStation-Hornet#10455

This has been in active use on prod since January 2024 with zero issues.

This works to address tgstation/dev-cycles-initiative#9 if it were to be implemented on TG