Approximation of tree incrementality for Z3 solver #815

Job	Run time
clang-format	2m 57s
Docker	2m 55s
Linux (LLVM 14)	2m 56s
Linux (LLVM 13)	2m 59s
Linux (LLVM 12)	2m 59s
Linux (LLVM 11, Doxygen)	2m 56s
Linux (LLVM 10)	2m 57s
Linux (LLVM 9)	2m 59s
Linux (ASan)	2m 59s
Linux (UBSan)	2m 53s
Linux (MSan)	2m 55s
Linux (Z3 only)	2m 56s
Linux (metaSMT)	2m 55s
Linux (STP master)	2m 56s
Linux (Latest klee-uclibc)	2m 59s
Linux (Asserts disabled)	2m 56s
Linux (No TCMalloc, optimised runtime)	2m 58s
Coverage (STP)	2m 58s
Coverage (Z3)	2m 58s
macOS	1s
	56m 2s

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