op-supernode/virtual_node: Update L1 genesis handling for genesis L2 block

[geoknee]

Clarify that for the genesis L2 block, we always return L1 block 0 without relying on the original configuration's L1 genesis. This allows for more flexibility in dispute game scenarios involving earlier L1 blocks.

Brings into line with this code

optimism/op-node/rollup/driver/sync_deriver.go

Lines 165 to 170 in db87881

	if s.SafeHeadNotifs.Enabled() && x.CrossSafe.ID() == s.Config.Genesis.L2 {
	// The rollup genesis block is always safe by definition. So if the pipeline resets this far back we know
	// we will process all safe head updates and can record genesis as always safe from L1 genesis.
	// Note that it is not safe to use cfg.Genesis.L1 here as it is the block immediately before the L2 genesis
	// but the contracts may have been deployed earlier than that, allowing creating a dispute game
	// with a L1 head prior to cfg.Genesis.L1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.2%. Comparing base (db87881) to head (f0f562b).

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #19114     +/-   ##
==========================================
+ Coverage     76.3%    77.2%   +0.9%     
==========================================
  Files          188      133     -55     
  Lines        10946     6916   -4030     
==========================================
- Hits          8360     5345   -3015     
+ Misses        2440     1571    -869     
+ Partials       146        0    -146     

Flag	Coverage Δ
cannon-go-tests-64	?
contracts-bedrock-tests	77.2% <ø> (-4.5%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.
see 64 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.