refactor: size optimizations, split native eth

[ozwaldorf]

Overall improves contract size by 50-55%.

Final erc20 escrow size: 8Kib
Final native eth escrow size: 7Kib

Changes

• Split native and erc20 into unique contracts
  • 15Kib -> 10 Kib native, 11Kib escrow
• Fix forge lints
  • erc20 transfer requires success response
  • hardcode runtime keccak computation
  • mark external-only functions as external
• Custom errors
  • ~2.2k bytes saved
• Inline constants
  • ~60 bytes saved
• Unchecked loops
  • ~7 bytes saved
• refactor: eliminate memory allocations in calldata parsing #18
  • ~600 bytes saved

Sol optimization attempt

Sol optimization passes at ~200 is near-optimal already for bytecode size:

• Tested with 10k optimization passes, contract size grew ~20% due to aggressive inlining.
• Tested with 1 optimization pass, contract size was only 7 bytes difference.

[g4titanx]

this is great tbh @ozwaldorf
i've got minor improvements to the proofs that will remove ~600 bytes and then we can merge this i guess, i'd open another pr now based off of this