feat(regtest): Add regtest halving interval and port test #1986

Job	Run time
Check deny.toml bans	28s
Check Cargo.lock is up to date	1m 4s
Install zebrad from lockfile without cache on ubuntu-latest	8m 8s
Check deny.toml bans --features default-release-binaries	34s
Test stable on ubuntu-latest	31m 37s
Check deny.toml bans --all-features	29s
Test beta on ubuntu-latest	40m 6s
Check for unused dependencies	57s
Test stable on macos-latest	32m 44s
Check deny.toml sources	32s
Test stable on windows-latest	1h 0m 10s
Check deny.toml sources --features default-release-binaries	28s
Test beta on windows-latest	1h 0m 17s
Check deny.toml sources --all-features	32s
Open or update issues for OS integration failures	0s
	3h 58m 6s

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