op-devstack: Fix challenger funding

[mbaxter]

Description

Fix op-devstack challenger funding logic.

There is currently a mismatch in how we fund challenger accounts and how we configure the challenger private key:

• The challenger, proposer, and other roles are funded in the context of an L2 chainId
• However, challenger private key is configured from an l1-specific key

This PR fixes this by setting the challenger's private key from a funded L2 challenger key.

Other changes:

• The WithSuperroots helper has been updated to use funded L2-specific keys for the proposer and challenger
• The L2ChallengerID has been updated to follow the same pattern as L2ChallengerID. This allows us to pull the correct chainId when configuring the challenger.

Metadata

Part of: #15948

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.10%. Comparing base (281a750) to head (08211fc).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #16419       +/-   ##
============================================
+ Coverage    47.02%   67.10%   +20.08%     
============================================
  Files         1389       55     -1334     
  Lines       112410     4299   -108111     
============================================
- Hits         52859     2885    -49974     
+ Misses       55827     1276    -54551     
+ Partials      3724      138     -3586     

Flag	Coverage Δ
cannon-go-tests-64	67.10% <ø> (ø)
contracts-bedrock-tests	?

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[Inphi]

Looks good.