Add transaction fee tests

[gztensor]

Description of the Change

Modified e2e tests to check that

• Non-zero transaction fee is applied for balance transfers
• No transaction fee is applied for add_stake extrinsic

Quantitative Performance Benefits

Not relevant. We don't have a template for adding tests.

Possible Drawbacks

If later we decide to lower transaction fees for balance transfers (e.g. to high TAO price), we will have to maintain this test.

Verification Process

Run:

LOCALNET_SH_PATH=<---=== replace with your path to subtensor repository===--- >/subtensor/scripts/localnet.sh pytest ./tests/e2e_tests/subcommands/wallet/test_transfer.py

LOCALNET_SH_PATH=<---=== replace with your path to subtensor repository===--- >/subtensor/scripts/localnet.sh pytest ./tests/e2e_tests/subcommands/stake/test_stake_add_remove.py

Applicable Issues

https://github.com/orgs/opentensor/projects/19/views/7?pane=issue&itemId=80965602

Release Notes

This is subtensor e2e test, no release notes should be added for BitTensor.