ci: move `nightly job` to the CI. #326

Job	Run time
set-image	1s
Check formatting	1m 7s
Check documentation	3m 59s
Build polkadot-staking-miner binary	7m 31s
Check code using cargo-hack	4m 41s
Clippy	5m 41s
Check staking-miner-playground	16m 48s
Run tests	2m 22s
Test Docker image build	0s
Build and publish Docker image	0s
	42m 10s

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