feat(SuperchainWETH): enable sending and relaying ETH via SuperchainWETH contract

[tremarkley]

Implements: ethereum-optimism/design-docs#146

Adds two new functions to the SuperchainWETH contract: sendETH and relayETH.

• sendETH: Deposits ETH in the ETHLiquidity contract and sends a message to the destination chain, encoding the relay details.
• relayETH: Withdraws the specified amount of ETH from ETHLiquidity on the destination chain and transfers it to the recipient.

This update streamlines L2-to-L2 ETH transfers, bypassing the need for separate wrapping and unwrapping steps. Notably, custom gas token chains are excluded from this simplification to maintain compatibility and reduce risk.

[tremarkley]

• feat(SuperchainWETH): enable sending and relaying ETH via SuperchainWETH contract #12710 👈 (View in Graphite)
• develop

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.71%. Comparing base (9200bff) to head (341ff25).
Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #12710      +/-   ##
===========================================
- Coverage    44.30%   42.71%   -1.59%     
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  Files          798      742      -56     
  Lines        71668    67003    -4665     
===========================================
- Hits         31751    28620    -3131     
+ Misses       37335    35972    -1363     
+ Partials      2582     2411     -171     

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[tynes]

I notice that the spec has not been updated: https://github.com/ethereum-optimism/specs/blob/main/specs/interop/superchain-weth.md