Refactor bdk-cli structure #1142

Job	Run time
Clippy (--all-features)	1m 12s
Build and test (stable, --features default)	26s
Build and test (stable, --all-features)	1m 30s
Clippy (--no-default-features)	17s
Build and test (stable, --no-default-features)	31s
Rust fmt	16s
	4m 12s

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