Use TaoBalance for pallet balances balance type

[gztensor]

Description

Replace u64 with TaoCurrency for pallet balances balance and all over the subtensor code.

Note: Manually tested on a baedeker clone: Out of 383695 account balances none changed after the runtime upgrade.

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): Cleanup

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

[ales-otf]

my comments are just stylistic preferences. additionally i didn't understand why you needed to add this _u64 specifier everywhere.

other than that i think this change is safe, because there is an entrypoint for this Balance type (the alias) so if you change it, the rest is compiler-driven refactoring. the inconsistency might appear only in places outside of this type or where we had a mixed type errors (alpha/tao used interchangeably). the first thing is unlikely for the balance value, the second can have a place. so far there still persists this issue with StakeThreshold, but i didn't see anything else in your PR

[l0r1s]

rhs == 0 panics, do we want to keep the behavior as close as possible to the normal one maybe?

[l0r1s]

Small remarks around the code that can panic.

It adds a lot of type safety and pave the way for more, great stuff!

Note for later: I was thinking about the naming of TaoCurrency and AlphaCurrency, a more appropriate name to match with Substrate primitives would be TaoBalance and AlphaBalance with the CustomBalance trait (as supertrait of Balance) because Currency as actually a full fledged system where you can make transfer, slash, burn, emit, etc...

[gztensor]

Small remarks around the code that can panic.

It adds a lot of type safety and pave the way for more, great stuff!

Note for later: I was thinking about the naming of TaoCurrency and AlphaCurrency, a more appropriate name to match with Substrate primitives would be TaoBalance and AlphaBalance with the CustomBalance trait (as supertrait of Balance) because Currency as actually a full fledged system where you can make transfer, slash, burn, emit, etc...

Good point! I renamed the following:

Currency -> Token
AlphaCurrency -> AlphaBalance
TaoCurrency -> TaoBalance
CurrencyReserve -> TokenReserve