docs: document persist_test_utils module #16

Job	Run time
Rust fmt	13s
prepare	6s
Rust clippy	1m 23s
Build & Test (ubuntu-24.04-arm, 1.88.0, true, --all-features)	1m 3s
Check no_std	21s
Build & Test (ubuntu-latest, 1.63.0, --no-default-features --features miniscript/no-std,bdk_chain...	5m 0s
Build & Test (ubuntu-latest, 1.63.0, --all-features)	5m 4s
Build & Test (ubuntu-24.04-arm, 1.63.0, --no-default-features --features miniscript/no-std,bdk_ch...	5m 12s
Build & Test (ubuntu-latest, 1.88.0, true, --no-default-features --features miniscript/no-std,bdk...	1m 58s
Build & Test Examples (example_wallet_electrum)	59s
Build & Test (ubuntu-24.04-arm, 1.88.0, true, --no-default-features --features miniscript/no-std,...	1m 16s
Build & Test (ubuntu-24.04-arm, 1.63.0, --all-features)	4m 29s
Build & Test Examples (example_wallet_esplora_async)	53s
Check WASM	1m 24s
Build & Test (ubuntu-latest, 1.88.0, true, --all-features)	1m 51s
Build & Test Examples (example_wallet_esplora_blocking)	50s
Build & Test Examples (example_wallet_rpc)	28s
	32m 30s

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