Change solochain flag into subcommand #4195

Job	Run time
set-tags	4s
cargo-toml-feature-propagation	1m 53s
cargo-clippy	2m 57s
Check with rustfmt	12s
check-copyright	3s
toml-formatting	50s
typescript-formatting	21s
typescript-linting	20s
build	4m 45s
typescript-tests-flashbox	3m 52s
check-api-augment	55s
rust-test	5m 45s
typescript-tests	4m 23s
typescript-tests-frontier	4m 3s
typescript-dancebox-specs	25s
typescript-tests-relay	5m 40s
typescript-tests-simple-template	2m 24s
zombienet-tests (zombie_tanssi)	10m 13s
zombienet-tests (zombie_tanssi_parathreads)	11m 40s
docker-tanssi (tanssi)	39s
chopsticks-upgrade-test (stagenet_dancebox, dancebox)	58s
docker-tanssi (container-chain-simple-template)	42s
chopsticks-upgrade-test (flashbox, flashbox)	1m 26s
docker-tanssi (container-chain-evm-template)	57s
chopsticks-upgrade-test (dancebox, dancebox)	52s
zombienet-tests (zombie_tanssi_rotation)	9m 13s
chopsticks-upgrade-test (frontier_template, container-chain-template-frontier)	49s
zombienet-tests (zombie_tanssi_warp_sync)	5m 29s
zombienet-tests (zombie_tanssi_relay)	10m 10s
zombienet-test-upgrade (dancebox)	4m 0s
zombienet-tests (zombie_data_preservers)	5m 32s
zombienet-test-upgrade-containers (frontier_template, container-chain-template-frontier)	27s
zombienet-test-upgrade-containers (simple_template, container-chain-template-simple)	1s
	1h 42m 0s

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