Refactor bdk-cli structure #1118

Job	Run time
Build and test (stable, --all-features)	1m 33s
Clippy (--no-default-features)	43s
Clippy (--all-features)	1m 2s
Build and test (stable, --features default)	55s
Build and test (stable, --no-default-features)	56s
Rust fmt	11s
	5m 20s

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