add(mining): Restore internal miner #2674

Job	Run time
Check deny.toml bans	47s
Check Cargo.lock is up to date	1m 19s
Check deny.toml bans --features default-release-binaries	45s
Check deny.toml bans --all-features	44s
Check deny.toml sources	43s
Install zebrad from lockfile without cache on ubuntu-latest	8m 30s
Check deny.toml sources --features default-release-binaries	42s
Check deny.toml sources --all-features	43s
Test stable on ubuntu-latest	33m 24s
Check for unused dependencies	6s
Test beta on ubuntu-latest	33m 1s
Test stable on macos-latest	37m 46s
Test stable on windows-latest	1h 3m 19s
Test beta on windows-latest	1h 3m 32s
Open or update issues for OS integration failures	0s
	4h 5m 21s

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