message: [Refactor] Rename scriptPubKey -> exec_script
  Rename misleading scriptPubKey in ExecuteWitnessScript() function to
  correctly relfect what is being executed.
diff: @@ -1815,16 +1815,16 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq
  template class GenericTransactionSignatureChecker<CTransaction>;
  template class GenericTransactionSignatureChecker<CMutableTransaction>;
  -static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CScript& scriptPubKey, unsigned int flags, SigVersion sigversion, const BaseSignatureChecker& checker, ScriptExecutionData& execdata, ScriptError* serror)
  +static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CScript& exec_script, unsigned int flags, SigVersion sigversion, const BaseSignatureChecker& checker, ScriptExecutionData& execdata, ScriptError* serror)
  {
  std::vector<valtype> stack{stack_span.begin(), stack_span.end()};
  if (sigversion == SigVersion::TAPSCRIPT) {
  // OP_SUCCESSx processing overrides everything, including stack element size limits
  - CScript::const_iterator pc = scriptPubKey.begin();
  - while (pc < scriptPubKey.end()) {
  + CScript::const_iterator pc = exec_script.begin();
  + while (pc < exec_script.end()) {
  opcodetype opcode;
  - if (!scriptPubKey.GetOp(pc, opcode)) {
  + if (!exec_script.GetOp(pc, opcode)) {
  // Note how this condition would not be reached if an unknown OP_SUCCESSx was found
  return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
  }
  @@ -1847,7 +1847,7 @@ static bool ExecuteWitnessScript(const Span<const valtype>& stack_span, const CS
  }
  // Run the script interpreter.
  - if (!EvalScript(stack, scriptPubKey, flags, checker, sigversion, execdata, serror)) return false;
  + if (!EvalScript(stack, exec_script, flags, checker, sigversion, execdata, serror)) return false;
  // Scripts inside witness implicitly require cleanstack behaviour
  if (stack.size() != 1) return set_error(serror, SCRIPT_ERR_CLEANSTACK);
  