feat: added `electrum` and `esplora` support to `TestEnv` #24

Job	Run time
Check WASM	54s
Check no_std	22s
clippy_check	4m 35s
Build and test (stable, true, --no-default-features)	3m 25s
Build and test (stable, true, --all-features)	3m 5s
Rust fmt	6s
Build and test (1.57.0, --no-default-features)	5m 38s
Build and test (1.57.0, --all-features)	6m 39s
	24m 44s

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