[MatusKysel]

Summary

• Keep super-instruction fallback inside the main interpreter loop instead of executing decomposed opcodes through a side helper.
• Preserve normal per-opcode behavior during fallback, including tracing and EIP-4762 code-chunk charging.
• Add regression coverage for fallback execution, opcode tracing, and Verkle code-chunk accounting.

Motivation

When a fused opcode falls back to its raw opcode sequence, the interpreter should continue execution exactly as if the unfused opcodes had been stepped normally.

The previous fallback path executed decomposed opcodes outside the main loop. That made control flow continue, but it bypassed main-loop behavior that is consensus- and tooling-relevant:

• OnOpcode tracing for fallback-executed opcodes
• EIP-4762 code-chunk charging/access-event updates on each stepped opcode

This change routes fallback through the existing interpreter loop so raw opcodes inherit the same gas, tracing, and PC progression semantics as normal execution.

Implementation

• Add a fallback []OpCode queue in the interpreter loop.
• When a fused opcode cannot pay its fused gas cost, decompose it and continue the loop in fallback mode.
• Step decomposed opcodes through the normal opcode path, then drain the fallback queue as each opcode completes.
• Remove the old helper that executed fallback opcodes out-of-band.