feat: add utilities for testing persistence #22

Job	Run time
prepare	5s
Rust fmt	18s
Build & Test (1.63.0, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 40s
Check no_std	18s
Build & Test (1.63.0, --all-features)	3m 45s
Build & Test (1.75.0, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 10s
Rust clippy	31s
Build & Test Examples (example_cli)	19s
Check WASM	59s
Build & Test (1.88.0, true, --all-features)	3m 30s
Build & Test Examples (example_esplora)	53s
Build & Test (1.75.0, --all-features)	3m 41s
Build & Test Examples (example_bitcoind_rpc_polling)	36s
Build & Test Examples (example_electrum)	56s
Build & Test (1.88.0, true, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 3s
	19m 44s

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