feat(contracts): validate l2ChainIds in OPContractsManagerMigrator.migrate

[stevennevins]

Description

OPContractsManagerMigrator.migrate checks that every supplied chain has the same ProxyAdmin owner and the same SuperchainConfig, but it never checks SystemConfig.l2ChainId() or requires the migrated chain IDs to be unique.

That missing precondition is dangerous after the portals share one super-root dispute game system. For super game types, OptimismPortal2.proveWithdrawalTransaction extracts the output root with rootClaimByChainId(systemConfig.l2ChainId()). If two migrated portals report the same chain ID, both portals select the same output root from the same shared game.

Changes

This change adds three new errors (OPContractsManagerMigrator_ZeroL2ChainId, OPContractsManagerMigrator_DuplicateL2ChainId, OPContractsManagerMigrator_ChainIdsNotAscending) and requires chainSystemConfigs to be supplied with non-zero and in ascending order;
The existing per-chain checks are moved into a new _validateChainSystemConfigs helper to keep migrate() under the stack-too-deep limit.

Tests

Tests now cover zero, duplicate, unsorted, and single-chain-zero cases
All existing migrate tests continue to pass.

fixes #20882

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.0%. Comparing base (6e38f8a) to head (d47a178).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #20926     +/-   ##
==========================================
+ Coverage     76.3%    82.0%   +5.7%     
==========================================
  Files          185      130     -55     
  Lines        10698     6674   -4024     
==========================================
- Hits          8166     5478   -2688     
+ Misses        2388     1196   -1192     
+ Partials       144        0    -144     

Flag	Coverage Δ
cannon-go-tests-64	?
contracts-bedrock-tests	82.0% <100.0%> (-0.4%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...bedrock/src/L1/opcm/OPContractsManagerMigrator.sol	98.7% <100.0%> (+0.1%)	⬆️

... and 56 files with indirect coverage changes

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[maurelian]

This LGTM.

[stevennevins]

/piper