refactor(eth): replace deprecated SignedIntValueEncoder with UintValu…

[expertdicer]

…eEncoder

Abstract

• Closes [bug] The IntKeyEncoder.Encode function panics if the input math.Int is nil or negative.  #2491

collections.IntValueEncoder used to delegate to IntKeyEncoder, which panics on negative or nil sdkmath.Int values. That was misleading for signed state (e.g. wei block deltas) and unsafe for callers that expected a general signed int encoder.

This PR splits signed value encoding from unsigned fixed-width encoding: IntValueEncoder now marshals signed sdkmath.Int, a new UintValueEncoder keeps the existing 32-byte big-endian format for non-negative persisted state, and weiStore is typed as sdkmath.Uint. eth.SignedIntValueEncoder is removed in favor of the generic collections encoder.

[codecov]

Codecov Report

❌ Patch coverage is 83.87097% with 5 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
x/collections/value_encoder.go	79.16%	3 Missing and 2 partials ⚠️

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