feat: add utilities for testing persistence #50

Job	Run time
Rust fmt	24s
prepare	4s
Check no_std	20s
Rust clippy	26s
Build & Test Examples (example_cli)	21s
Check WASM	38s
Build & Test (1.94.1, --no-default-features --features bdk_chain/hashbrown)	1m 36s
Build & Test (1.94.1, --all-features)	3m 30s
Build & Test Examples (example_electrum)	47s
Check documentation errors	26s
Build & Test Examples (example_bitcoind_rpc_polling)	34s
Build & Test Examples (example_esplora)	43s
Build & Test (1.85.0, --no-default-features --features bdk_chain/hashbrown)	1m 50s
Build & Test (1.85.0, --all-features)	3m 51s
	15m 30s

Provide feedback