refactor(fuzzer): share coverage counter registration #27

Job	Run time
create prebuilds (ubuntu-24.04-arm)	57s
create prebuilds (windows-latest)	3m 14s
create prebuilds (macos-latest, --arch x86_64)	3m 17s
create prebuilds (ubuntu-latest)	50s
create prebuilds (macos-latest)	2m 6s
verify prebuilds	4s
publish	18s
	10m 46s

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