docs: add v104 migration guide

[rakita]

Summary

• Adds migration guide for v104 tag (revm v34.1.0) covering all breaking changes and new features
• Covers bytecode flattening, ResultGas, logs on revert/halt, EIP-161 state clear changes, Amsterdam hardfork features (EIP-7843, EIP-7708, EIP-8024), and more

Test plan

• Verify markdown renders correctly on GitHub

[codspeed-hq]

Merging this PR will not alter performance

✅ 176 untouched benchmarks

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_{Comparing docs/v104-migration-guide (3b40de0) with main (78a8ff6)}