refactor(wallet): use `Amount` everywhere #6031

Job	Run time
Check no_std	46s
Build and test (stable, true, --no-default-features)	3m 49s
Check WASM	52s
Build and test (stable, true, --all-features)	3m 55s
prepare	3s
Build and test (1.63.0, --no-default-features)	5m 4s
Build and test (1.63.0, --all-features)	5m 7s
Build Examples (example_cli)	30s
Rust fmt	12s
Build Examples (example_bitcoind_rpc_polling)	42s
Build Examples (example_electrum)	1m 3s
Build Examples (example_esplora)	53s
Build Examples (wallet_electrum)	58s
Build Examples (wallet_esplora_async)	58s
Build Examples (wallet_esplora_blocking)	53s
Build Examples (wallet_rpc)	41s
clippy_check	1m 20s
	27m 46s

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