refactor(wallet): cleanup and remove unused code in create_tx #6551

Job	Run time
prepare	4s
Rust fmt	14s
Check no_std	42s
Build & Test Examples (example_cli)	43s
Build and test (1.83.0, true, --no-default-features --features miniscript/no-std)	2m 15s
Check WASM	57s
Build and test (1.83.0, true, --all-features)	3m 45s
clippy_check	1m 17s
Build and test (1.63.0, --no-default-features --features miniscript/no-std)	3m 38s
Build & Test Examples (example_bitcoind_rpc_polling)	38s
Build and test (1.63.0, --all-features)	5m 14s
Build & Test Examples (example_electrum)	51s
Build & Test Examples (example_esplora)	52s
Build & Test Examples (example_wallet_electrum)	51s
Build & Test Examples (example_wallet_esplora_async)	57s
Build & Test Examples (example_wallet_esplora_blocking)	51s
Build & Test Examples (example_wallet_rpc)	37s
	24m 26s

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