fuzz: model chanmon mempool mining #23492

Job	Run time
ext-test	8m 51s
benchmark	17m 48s
check_docs	5m 19s
check_release	2m 55s
linting	2m 41s
fuzz_sanity	17m 11s
tor-connect	7m 48s
fuzz	58m 59s
rustfmt	14s
build-nostd / build (self-hosted, 1.75.0)	20m 31s
build-cfg-flags / build (self-hosted, 1.75.0)	18m 24s
build-workspace / build (self-hosted, 1.75.0)	13m 43s
build-features / build (self-hosted, 1.75.0)	35m 53s
build-bindings / build (self-hosted, 1.75.0)	58m 59s
build-sync / build (self-hosted, 1.75.0)	26m 37s
	4h 55m 53s

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