feat: Add Transaction input/output helper methods and extreme tx test

[JAGADISHSUNILPEDNEKAR]

Summary

This PR implements helper methods for the Transaction class to simplify input and output management, addressing several TODO items. It also adds a new test case for transactions with a large number of outputs to verify serialization limits.

Changes

• bitcoinutils/transactions.py:
  • Added add_input, update_input, remove_input
  • Added add_output, update_output, remove_output
  • Ensure add_input automatically adds an empty witness when has_segwit is True, keeping the lists synchronized.
• tests/test_transaction_helpers.py: New unit tests for the helper methods.
• tests/test_extreme_txs.py: New test case creating a transaction with 260 outputs.

Motivation

• Addresses TODO item: "think how to add/remove existing inputs/outputs to a Tx object"
• Addresses TODO item: "create test with 260 outputs"
• Improves usability and safety by preventing mismatched inputs/witnesses lists.

Verification

• Added new tests in tests/test_transaction_helpers.py and tests/test_extreme_txs.py.
• Ran full test suite via python -m unittest discover tests/ and all 103 tests passed.