Rework multibyte opcode support

[sorpaas]

• Removed the Opcode parameter from Efn -- when there are multibyte opcode this becomes confusing, plus the single byte Opcode can be easily fetched as machine.code()[position].
• Added MultiEtable, where each item can itself be another etable. During evaluation the extra position change will be added by the "parent" node.

[Copilot]

Pull Request Overview

This PR refactors opcode dispatch to support multibyte opcodes by removing the explicit Opcode parameter from evaluation functions and introducing composable etable types (Single, Chained, and MultiEtable).

• Remove the Opcode argument from all eval function signatures and bypass single‐byte tables.
• Add Single for single‐function etables, Chained for combining two etables, and MultiEtable for nested opcode tables.
• Update tests and interpreter core to use the new etable API.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/eip_6780.rs	Updated tests to use Single::new and Chained etable API
src/standard/gasometer/mod.rs	Removed old opcode parameter and changed NextEtable to NoAction
jsontests/src/run.rs	Updated JSON tests to use Single::new and Chained
interpreter/tests/usability.rs	Added MultiEtable usage and refactored wrap closures
interpreter/src/interpreter/etable.rs	Changed interpreter loop to call etable.eval(position)
interpreter/src/eval/mod.rs	Removed unused _opcode parameters from all eval functions
interpreter/src/etable.rs	Introduced Single, Chained, MultiEfn, MultiEtable, and updated EtableSet API
interpreter/src/error/exit.rs	Deleted obsolete UnknownEtable variant

[Copilot]

Throwing PCUnderflow when the next position exceeds the code length seems incorrect; out-of-bounds positions should raise a PCOverflow exception instead.

Suggested change

	return Control::Exit(ExitException::PCUnderflow.into());
	return Control::Exit(ExitException::PCOverflow.into());