Add OVM_L1BlockNumber predeploy

[mslipper]

Meta:

• Fixes ENG-2139

[codecov-commenter]

Codecov Report

Merging #431 (75a23e7) into main (a087de8) will increase coverage by 3.31%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #431      +/-   ##
==========================================
+ Coverage   50.06%   53.38%   +3.31%     
==========================================
  Files          51       62      +11     
  Lines        5151     6481    +1330     
==========================================
+ Hits         2579     3460     +881     
- Misses       2240     2585     +345     
- Partials      332      436     +104     

Impacted Files	Coverage Δ
opnode/internal/testlog/testlog.go	58.46% <0.00%> (-9.24%)	:arrow_down:
opnode/rollup/driver/state.go	71.23% <0.00%> (-6.55%)	:arrow_down:
l2os/l2_output_submitter.go	48.22% <0.00%> (-5.32%)	:arrow_down:
opnode/node/node.go	60.00% <0.00%> (-4.25%)	:arrow_down:
opnode/rollup/driver/step.go	61.37% <0.00%> (-3.13%)	:arrow_down:
opnode/p2p/config.go	7.83% <0.00%> (-0.18%)	:arrow_down:
l2os/config.go	0.00% <0.00%> (ø)
opnode/service.go	0.00% <0.00%> (ø)
opnode/eth/heads.go	69.56% <0.00%> (ø)
opnode/node/config.go	33.33% <0.00%> (ø)
... and 29 more

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[tynes]

I have a preference for leaving the L2 folder flat, in its current form the other contracts that are in there are also predeploys but not in L2/predeploys