message: fix: improve signOrigin oversign check; fields which are not a MessageSignature don't count in overlap check
diff: -import { StacksTransaction } from './transaction';
  +import { StacksTransaction, StacksMessageType } from './transaction';
  import { StacksPrivateKey, StacksPublicKey } from './keys';
  import { isSingleSig, SpendingConditionOpts } from './authorization';
  @@ -56,7 +56,7 @@ export class TransactionSigner {
  const spendingCondition = this.transaction.auth.spendingCondition;
  if (
  this.checkOversign &&
  - spendingCondition.fields.length >= spendingCondition.signaturesRequired
  + spendingCondition.fields.filter((field) => field.contents.type === StacksMessageType.MessageSignature).length >= spendingCondition.signaturesRequired
  ) {
  throw new Error('Origin would have too many signatures');
  }
  