add(consensus/network): Add an empty `Parameters` struct in `Network::Testnet` #1057

Job	Run time
Test stable on ubuntu-latest	31m 12s
Check Cargo.lock is up to date	1m 48s
Test beta on ubuntu-latest	29m 40s
Install zebrad from lockfile without cache on ubuntu-latest	9m 30s
Test stable on macos-latest	1h 14m 38s
Check deny.toml bans	1m 54s
Check for unused dependencies	23s
Check deny.toml bans --features default-release-binaries	1m 53s
Check deny.toml bans --all-features	44s
Check deny.toml sources	41s
Check deny.toml sources --features default-release-binaries	39s
Check deny.toml sources --all-features	39s
Open or update issues for OS integration failures	0s
	2h 33m 41s

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