chore: centralise weight calculation and reduce writes to storage

[darrenkel]

Description

• housekeeping: accumulate all validators totals updates, so we only write once per total
• weights: centralise weight calculation using new stakes package

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• 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
• New and existing E2E tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 12.08054% with 131 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.15%. Comparing base (f03d35e) to head (2db7720).

Files with missing lines	Patch %	Lines
builtin/staker/validation/validation.go	0.00%	34 Missing ⚠️
builtin/staker/delta/delta.go	0.00%	25 Missing ⚠️
builtin/staker/globalstats/service.go	0.00%	25 Missing ⚠️
builtin/staker/stakes/stakes.go	0.00%	11 Missing ⚠️
builtin/staker/validation/service.go	0.00%	10 Missing ⚠️
builtin/staker/aggregation/service.go	0.00%	9 Missing ⚠️
builtin/staker/housekeep.go	44.44%	2 Missing and 3 partials ⚠️
builtin/staker/staker.go	68.75%	0 Missing and 5 partials ⚠️
builtin/staker/delegation/service.go	0.00%	4 Missing ⚠️
builtin/staker/delegation/delegation.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##           release/hayabusa    #1210      +/-   ##
====================================================
- Coverage             58.21%   58.15%   -0.07%     
====================================================
  Files                   275      277       +2     
  Lines                 28987    29014      +27     
====================================================
- Hits                  16876    16872       -4     
- Misses                10675    10706      +31     
  Partials               1436     1436              

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[otherview]

I think this is on the right path.
It seems like the goal is to abstract away the concept of Stake (big.Int) and replace it with Weighted Stake (struct).
This avoids any miscalculation or misuse of the stake vs weight.

What about making the Stake a private field and only allowing the access of the WeightedStake ?
My concern is that the Stake can be changed directly wrongfully.
Perhaps, as an example, if the delegation moved from delegation.Stake + delegation.Multiplier to delegation.WeightedStake then it should be impossible to mess that up.

[otherview]

Perhaps worth making the SetDelegation to a private method. Not a block imo