Integrate FreeType with alternative rendering engines

Investigate and implement alternative font renderers in FreeType, including: • font-rs: A font renderer developed by Raph Levien. A blogpost describes some of its features in more detail. It claims to be much faster than FreeType's anti-aliasing rendering module by using different data structures, SIMD optimizations etc. • font-go: Port of font-rs to the Go programming language, includes a fixed-point implementation that is allegedly 1.4 times faster. • fontdue: It is another rendering engine based on font-rs, and it claims to be even faster and is actively developed. Additional discussion can be found here. • Pathfinder: Another project inspired by font-rs is Pathfinder, which takes advantages of GPU rendering. The project involves continuing and eventually finalizing the GSoC 2022 contribution, including but not limited to improving build system support, adding SIMD optimizations to more processors, improving documentation etc