Instrumentation for delayed UB stemming from uninitialized memory #7462

Job	Run time
benchcomp-tests	4m 30s
perf	30m 40s
regression (macos-13)	35m 14s
write-json-symtab-regression	18m 9s
regression (ubuntu-20.04)	27m 9s
regression (ubuntu-22.04)	27m 37s
regression (macos-14)	19m 14s
documentation	2m 2s
	2h 44m 35s

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