eth_call with state overrides

[koko1123]

Summary

Add support for eth_call state overrides, allowing users to simulate transactions against modified blockchain state without forking a node.

Motivation

Searchers need to simulate "what if" scenarios: what if this token balance was X? What if this pool had Y liquidity? State overrides let you answer these questions with a single RPC call instead of running a local fork.

This is critical for:

• Simulating sandwich attacks with modified token balances
• Testing liquidation scenarios with modified collateral ratios
• Evaluating arb profitability under different pool states

Proposed API

const eth = @import("eth");

// Override state for a specific contract
var overrides = eth.provider.StateOverrides.init(allocator);
defer overrides.deinit();

try overrides.setBalance(target_address, new_balance);
try overrides.setStorageAt(pool_address, slot, new_value);
try overrides.setCode(contract_address, new_bytecode);

const result = try provider.call(.{
    .to = target,
    .data = calldata,
}, .{ .state_overrides = &overrides });

Implementation Notes

• Maps to the stateOverride parameter in eth_call (Geth docs)
• Support overriding: balance, nonce, code, state (full storage), stateDiff (partial storage)
• Should compose with batch eth_call (Deprecated allocator initialization + tests fix LLVM crash by AI  #10)
• Most L2 RPC providers support state overrides (Alchemy, Infura, QuickNode)

References

• Geth state override docs