Revert "use subxt-signer to reduce the number of deps (#720)" (#743) #282

Job	Run time
set-image	1s
Check formatting	1m 6s
Build polkadot-staking-miner binary	6m 17s
Clippy	4m 48s
Check code using cargo-hack	6m 17s
Check documentation	3m 11s
Check staking-miner-playground	6m 18s
Run tests	5m 41s
Build and publish Docker image	1s
Test Docker image build	1s
	33m 41s

Provide feedback