fix(load): only modify non-reserved slots

[RodrigoVillar]

Why this should be merged

As mentioned in #4245, there's currently a flake in the load test where the following error(s) will appear early on:

[09-16|17:10:45.042] ERROR tests/simple_test_context.go:57 
        Error Trace:    /Users/rodrigo.villar/go/src/github.com/ava-labs/avalanchego/tests/load/tests.go:375
                                                /Users/rodrigo.villar/go/src/github.com/ava-labs/avalanchego/tests/load/tests.go:297
                                                /Users/rodrigo.villar/go/src/github.com/ava-labs/avalanchego/tests/load/tests.go:213
                                                /Users/rodrigo.villar/go/src/github.com/ava-labs/avalanchego/tests/load/generator.go:103
                                                /Users/rodrigo.villar/go/src/github.com/ava-labs/avalanchego/tests/load/generator.go:87
                                                /Users/rodrigo.villar/go/1.23.9/pkg/mod/golang.org/x/sync@v0.12.0/errgroup/errgroup.go:78
                                                /Users/rodrigo.villar/.goenv/versions/1.23.9/src/runtime/asm_arm64.s:1223
        Error:          Received unexpected error:
                        transaction accepted but failed to execute entirely

This error occurs frequently when setting the number of workers to a high value. After some debugging, it appears that the source of this error is from execution of ModifyTest. Looking at modify()(which ModifyTest calls) in the simulator contract, the current implementation is flawed in that it is allows for modifications of the first two storage slots, which should never happen.

The consequence of this current implementation is a transaction could set latestEmptySlot to an arbitrarily high value, which could result in subsequent transactions failing due to writing to empty slots (via running out of gas), as opposed to writing to non-empty slots.

How this works

Updates modify() to never modify the first 2 contract slots.

How this was tested

CI + ran load test locally with high number of workers

Need to be documented in RELEASES.md?

No

[Copilot]

Pull Request Overview

This PR fixes a flake in the load test by preventing the modify() function from modifying reserved storage slots (first two slots). The issue was causing transactions to fail when latestEmptySlot was set to arbitrarily high values.

• Updates the assembly code in the modify() function to skip the first 2 contract storage slots
• Adds an offset to ensure modifications only occur on non-reserved slots
• Regenerates the contract bindings to reflect the code changes

Reviewed Changes

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

File	Description
tests/load/contracts/LoadSimulator.sol	Updates modify() function assembly to skip first 2 storage slots
tests/load/contracts/LoadSimulator.bindings.go	Regenerated Go bindings with updated contract bytecode

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