refactor(wallet): cleanup and remove unused code in create_tx #1401

Job	Run time
Check no_std	10s
Build and test (stable, true, --no-default-features --features miniscript/no-std)	2m 18s
Check WASM	33s
Build and test (stable, true, --all-features)	4m 7s
Rust fmt	13s
Build and test (1.63.0, --no-default-features --features miniscript/no-std)	3m 16s
prepare	5s
Build and test (1.63.0, --all-features)	5m 26s
Build & Test Examples (example_cli)	25s
Build & Test Examples (example_bitcoind_rpc_polling)	48s
Build & Test Examples (example_electrum)	52s
Build & Test Examples (example_esplora)	58s
Build & Test Examples (example_wallet_electrum)	47s
Build & Test Examples (example_wallet_esplora_async)	57s
Build & Test Examples (example_wallet_esplora_blocking)	52s
Build & Test Examples (example_wallet_rpc)	24s
clippy_check	1m 3s
	23m 14s

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