Improved Iterative Deepening Searcher #891

Job	Run time
clang-format	5m 35s
Docker	18m 2s
Coverage (STP)	51m 33s
Coverage (Z3)	43m 40s
Linux (LLVM 14)	16m 27s
macOS	12m 1s
Linux (LLVM 13)	16m 29s
Linux (LLVM 12)	18m 43s
Linux (LLVM 11, Doxygen)	17m 41s
Linux (LLVM 10)	18m 14s
Linux (LLVM 9)	15m 9s
Linux (ASan)	52m 27s
Linux (UBSan)	47m 16s
Linux (MSan)	1h 8m 53s
Linux (Z3 only)	16m 49s
Linux (metaSMT)	34m 16s
Linux (STP master)	17m 47s
Linux (Latest klee-uclibc)	18m 56s
Linux (Asserts disabled)	17m 8s
Linux (No TCMalloc, optimised runtime)	16m 18s
	8h 43m 24s

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