Change coin_selection and DescriptorExt::dust_value to use Amount type #6458

Job	Run time
Check WASM	41s
Check no_std	29s
Build & Test Examples (example_cli)	35s
Build and test (stable, true, --no-default-features --features miniscript/no-std)	1m 58s
Rust fmt	10s
Build & Test Examples (example_bitcoind_rpc_polling)	25s
prepare	7s
Build and test (stable, true, --all-features)	3m 54s
Build and test (1.63.0, --no-default-features --features miniscript/no-std)	2m 20s
Build & Test Examples (example_electrum)	53s
Build and test (1.63.0, --all-features)	4m 47s
Build & Test Examples (example_esplora)	59s
Build & Test Examples (example_wallet_electrum)	56s
Build & Test Examples (example_wallet_esplora_async)	1m 1s
Build & Test Examples (example_wallet_esplora_blocking)	45s
Build & Test Examples (example_wallet_rpc)	54s
clippy_check	59s
	21m 53s

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