chore(sdk-coin-apt): add getter for seq no. in tx builder

TICKET: COIN-3450

Author: bhavidhingra

modules/sdk-coin-apt/src/lib/transactionBuilder/transactionBuilder.ts

@@ -28,6 +28,10 @@ export abstract class TransactionBuilder extends BaseTransactionBuilder {
    */
   protected abstract get transactionType(): TransactionType;
 
+  getSequenceNumber(): number {
+    return this.transaction.sequenceNumber;
+  }
+
   /**
    * Initialize the transaction builder fields using the decoded transaction data
    *

modules/sdk-coin-apt/test/unit/transactionBuilder/transferBuilder.ts

@@ -52,6 +52,8 @@ describe('Apt Transfer Transaction', () => {
 
       it('should build and send a signed tx', async function () {
         const txBuilder = factory.from(testData.TRANSACTION_USING_TRANSFER_COINS);
+        txBuilder.getSequenceNumber().should.equal(146);
+
         const tx = (await txBuilder.build()) as TransferTransaction;
         should.equal(tx.type, TransactionType.Send);
         tx.inputs.length.should.equal(1);