Introduce ERC-8100 Standard for Representable Contract State

ERC-8100 introduces IXMLRepresentableState, an XML-based standard interface letting EVM contracts expose canonical state views. Off-chain renderers use eth_call at specific blocks without gas costs to build cryptographically anchored XML snapshots. Optional extensions add versioning and hashing. Use cases include smart derivatives, bonds, governance, and registries. Demo contracts like MinimalInstrument and InterestRateSwapSettleToMarket illustrate deployments within the evmstate namespace.