Revert "use subxt-signer to reduce the number of deps (#720)" #280

Job	Run time
set-image	1s
Build polkadot-staking-miner binary	8m 23s
Clippy	4m 42s
Check code using cargo-hack	6m 35s
Check documentation	3m 8s
Check staking-miner-playground	14m 22s
Check formatting	1m 3s
Run tests	5m 21s
Test Docker image build	16s
Build and publish Docker image	0s
	43m 51s

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