Function execute_script 

pub fn execute_script(
    script: &[u8],
    stack: &mut Vec<Vec<u8>>,
    transaction: &Transaction,
    input_index: usize,
    previous_value: u64,
    flags: ScriptFlags,
    signatures: &dyn SignatureVerifier,
) -> Result<(), ScriptError>

Execute one script against an existing stack. The caller retains the final stack, making this useful below witness-program policy while remaining bounded and independent of any async runtime or storage.