Pallet alpha-assets

[gztensor]

Description

• Add new pallet alpha-assets for handling total alpha issuance, alpha burned, and alpha recycled per netuid
• Integrate alpha-assets with subtensor pallet:
  • When alpha is emitted, emit as PositiveAlphaImbalance and resolve to SubnetAlphaIn and SubnetAlphaOut. This is the first step towards managing all internal alpha transactions via transfers and imbalances.

Part of #2636

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):

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