Major frontend refactor #1170

Job	Run time
preprocessor-host (gcc, riscv)	36s
host-arm (dynamic)	8m 16s
preprocessor-host (gcc, arm)	28s
coding-style	10s
preprocessor-host (clang, arm)	37s
host-arm (static)	10m 0s
preprocessor-host (clang, riscv)	34s
host-x86 (gcc, riscv, static)	53s
host-x86 (clang, riscv, static)	49s
host-x86 (gcc, arm, dynamic)	57s
host-x86 (clang, arm, static)	51s
host-x86 (clang, arm, dynamic)	59s
host-x86 (gcc, arm, static)	46s
	25m 56s

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