Improve coverage branches tests #1020

Job	Run time
clang-format	5m 47s
Docker	15m 28s
Coverage (STP)	37m 20s
Coverage (Z3)	37m 36s
macOS	13m 16s
Linux (LLVM 14)	11m 42s
Linux (LLVM 13)	10m 48s
Linux (LLVM 12)	10m 37s
Linux (LLVM 11, Doxygen)	10m 36s
Linux (LLVM 10)	10m 37s
Linux (LLVM 9)	10m 37s
Linux (ASan)	10m 36s
Linux (UBSan)	10m 36s
Linux (MSan)	10m 37s
Linux (Z3 only)	10m 37s
Linux (metaSMT)	10m 41s
Linux (STP master)	10m 37s
Linux (Latest klee-uclibc)	10m 35s
Linux (Asserts disabled)	10m 20s
Linux (No TCMalloc, optimised runtime)	11m 10s
	4h 30m 13s

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