fix(bytecode): skip DUPN/SWAPN/EXCHANGE immediates in analyze_legacy

[cuiweixie]

Summary

• Skip the 1-byte immediate of DUPN/SWAPN/EXCHANGE during legacy analysis (same as PUSH), so a JUMPDEST byte in that immediate is not marked as a valid jump target.
• Simplify end-of-bytecode padding: incomplete immediates are covered by iterator overflow; only append a final STOP when needed.
• Add regression tests for jump-table correctness and truncated opcode padding.

Test plan

• cargo test -p revm-bytecode --lib dupn_swapn -- --nocapture
• cargo test -p revm-bytecode --lib legacy::analysis::tests
• Confirm the two new tests fail if the skip branch is removed

[codspeed-hq]

Merging this PR will improve performance by 3.59%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 180 untouched benchmarks
⏩ 1 skipped benchmark¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	blake2/2_rounds	3.4 µs	3.2 µs	+3.59%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing cuiweixie:fix/analyze-legacy-dupn-swapn-exchange-immediate (83a6bf9) with main (a094a93)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩