Improve coverage branches tests #1027

Job	Run time
Docker	13m 1s
Coverage (STP)	38m 50s
Coverage (Z3)	52m 47s
Linux (LLVM 14)	19m 27s
Linux (LLVM 13)	19m 47s
clang-format	5m 48s
macOS	11m 2s
Linux (LLVM 12)	10m 57s
Linux (LLVM 11, Doxygen)	17m 19s
Linux (LLVM 10)	20m 42s
Linux (LLVM 9)	11m 11s
Linux (ASan)	48m 56s
Linux (UBSan)	48m 35s
Linux (MSan)	48m 55s
Linux (Z3 only)	21m 8s
Linux (metaSMT)	31m 46s
Linux (STP master)	9m 32s
Linux (Latest klee-uclibc)	10m 49s
Linux (Asserts disabled)	15m 20s
Linux (No TCMalloc, optimised runtime)	11m 14s
	7h 47m 6s

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