proof of concept: implement `cancel_tx` #6461

Job	Run time
Check no_std	36s
Check WASM	1m 16s
Rust fmt	7s
Build & Test Examples (example_cli)	34s
Build & Test Examples (example_bitcoind_rpc_polling)	30s
prepare	3s
Build and test (stable, true, --no-default-features --features miniscript/no-std)	2m 22s
Build & Test Examples (example_electrum)	45s
Build and test (stable, true, --all-features)	4m 6s
Build & Test Examples (example_esplora)	53s
Build and test (1.63.0, --no-default-features --features miniscript/no-std)	3m 1s
Build & Test Examples (example_wallet_electrum)	49s
Build and test (1.63.0, --all-features)	5m 12s
Build & Test Examples (example_wallet_esplora_async)	1m 5s
Build & Test Examples (example_wallet_esplora_blocking)	54s
Build & Test Examples (example_wallet_rpc)	38s
clippy_check	1m 11s
	24m 2s

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