Eval: Make counts and maxCounts simple values, not pointers

[jannotti]

Summary

This change makes it clearer that there is no sharing among the storageDeltas. There was no sharing, because each pointed to object was freshly allocated, but using a pointer obscured that fact (and performed a wasted allocation.

This change will make it easier (or at least clearer) to make changes to maxCounts if we allow transactions that update an app's global schema.

Test Plan

[Copilot]

Pull Request Overview

This PR simplifies memory management by changing counts and maxCounts fields in storageDelta from pointers to simple values, eliminating unnecessary pointer allocations while clarifying that no sharing occurs between storage deltas.

• Changed counts and maxCounts fields from *basics.StateSchema to basics.StateSchema
• Updated all assignments and comparisons to work with value types instead of pointers
• Improved test assertions using require.ErrorContains for better readability

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
ledger/eval/appcow.go	Modified storageDelta struct to use value types and updated all field assignments
ledger/eval/appcow_test.go	Updated test code to work with value types and improved error assertions

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