Independent solver rework #757

Job	Run time
macOS	11m 33s
Coverage (STP)	29m 48s
Coverage (Z3)	41m 56s
Linux (LLVM 14)	13m 58s
Linux (LLVM 13)	14m 36s
Linux (LLVM 12)	14m 29s
Linux (LLVM 11, Doxygen)	17m 40s
Linux (LLVM 10)	16m 24s
Linux (LLVM 9)	14m 54s
Linux (ASan)	48m 58s
Linux (UBSan)	33m 58s
Linux (MSan)	45m 10s
Linux (Z3 only)	13m 20s
Linux (metaSMT)	33m 52s
Linux (STP master)	16m 36s
Linux (Latest klee-uclibc)	21m 1s
Linux (Asserts disabled)	13m 20s
Linux (No TCMalloc, optimised runtime)	17m 24s
clang-format	5m 58s
Docker	12m 49s
	7h 17m 44s

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