Independent solver rework #759

Job	Run time
clang-format	6m 35s
Docker	10m 8s
Coverage (STP)	36m 37s
Coverage (Z3)	33m 21s
Linux (LLVM 14)	14m 32s
Linux (LLVM 13)	13m 34s
Linux (LLVM 12)	17m 9s
Linux (LLVM 11, Doxygen)	17m 16s
Linux (LLVM 10)	13m 32s
Linux (LLVM 9)	20m 26s
Linux (ASan)	41m 10s
Linux (UBSan)	34m 38s
Linux (MSan)	45m 2s
Linux (Z3 only)	12m 53s
Linux (metaSMT)	39m 21s
Linux (STP master)	13m 46s
Linux (Latest klee-uclibc)	18m 3s
Linux (Asserts disabled)	12m 50s
Linux (No TCMalloc, optimised runtime)	12m 42s
macOS	10m 17s
	7h 3m 52s

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