feat: complete TangleClient, generalize services, contexts #17

Job	Run time
Rustfmt	14s
cargo clippy	1m 28s
cargo test (gadget-blueprint-serde)	1m 42s
cargo test (gadget-clients)	1m 21s
cargo test (gadget-contexts)	1m 17s
cargo test (gadget-crypto)	1m 36s
cargo test (gadget-crypto-core)	1s
cargo test (gadget-crypto-sp-core)	1s
cargo test (gadget-crypto-ed25519)	1s
cargo test (gadget-crypto-bls)	1s
cargo test (gadget-crypto-k256)	1s
cargo test (gadget-crypto-sr25519)	1s
cargo test (gadget-crypto-tangle-pair-signer)	1s
cargo test (gadget-event-listeners-core)	1s
cargo test (gadget-event-listeners-evm)	1s
cargo test (gadget-event-listeners-periodic)	1s
cargo test (gadget-event-listeners-tangle)	1s
cargo test (gadget-keystore)	1s
cargo test (gadget-logging)	1s
cargo test (gadget-std)	1s
cargo test (gadget-utils-tangle)	1s
	7m 53s

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