Support negative heights in `HashOrHeight` #2681

Job	Run time
Check deny.toml bans	36s
Check deny.toml bans --features default-release-binaries	40s
Check Cargo.lock is up to date	55s
Check deny.toml bans --all-features	36s
Install zebrad from lockfile without cache on ubuntu-latest	8m 22s
Check deny.toml sources	38s
Test stable on ubuntu-latest	33m 38s
Check deny.toml sources --features default-release-binaries	39s
Test beta on ubuntu-latest	34m 5s
Check deny.toml sources --all-features	35s
Check for unused dependencies	7s
Test stable on macos-latest	37m 56s
Test stable on windows-latest	1h 4m 31s
Test beta on windows-latest	1h 5m 8s
Open or update issues for OS integration failures	0s
	4h 8m 26s

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