feat: add utilities for testing persistence #10

Job	Run time
prepare	5s
Rust fmt	16s
Check no_std	23s
Rust clippy	27s
Build & Test Examples (example_bitcoind_rpc_polling)	41s
Build & Test (1.63.0, --all-features)	1m 58s
Build & Test (1.87.0, true, --all-features)	1m 43s
Build & Test (1.75.0, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 58s
Build & Test (1.87.0, true, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 21s
Build & Test (1.75.0, --all-features)	1m 54s
Build & Test Examples (example_esplora)	56s
Check WASM	52s
Build & Test Examples (example_cli)	24s
Build & Test (1.63.0, --no-default-features --features miniscript/no-std,bdk_chain/hashbrown)	1m 58s
Build & Test Examples (example_electrum)	1m 3s
	15m 59s

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