Fix: Issue #1960 - Refactor InsufficientBalance error

[Q-YZX0]

Description

Refactored the generic InsufficientBalance error into specific NotEnoughBalanceToPayFee and NotEnoughBalanceToPayStake errors. This improves error granularity and debugging for subnet registration and staking operations.

Related Issue(s)

• Closes Separate pallets/subtensor/src/macros/errors.rs:InsufficientBalance to two type of errors. #1960

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

N/A

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

N/A

Additional Notes

Updated related tests in staking.rs to assert the new specific errors.