fix(L1): revert SuperchainConfig merger on v8.4.0

[jackchuma]

What changed? Why?

Revert #432 on releases/v8.4.0 to restore separate SuperchainConfig pause management. This reverses the actual squash merge a0b8955a33e51733940f3424cf84abc0fae2c071 across contracts, interfaces, deployment configuration and tooling, tests, ABI/storage snapshots, and semver hashes.

Notes to reviewers

• Targets releases/v8.4.0, not main. Preserve unrelated release changes from Use generic names for AggregateVerifier intervals #444, add cobalt reports #446, chore: improve smart account handling #447, and refactor(L2): tighten BaseTime NatSpec and tests #449, including AggregateVerifier/BaseTime snapshots and semver entries. The ETHLockbox removal from fix(L1): bump semver for contracts changed since the last release #438/fix(L1): bump SystemConfig semver for the ETHLockbox removal #440 remains intact.
• Restore the SuperchainConfig implementation/proxy/deployment stage, pause APIs and passthrough getters, the SuperchainConfig initializer argument/storage on SystemConfig, and the superchainConfigGuardian / superchainConfigIncidentResponder deploy keys.
• Resolve the overlapping OptimismPortal2 version change as 6.0.1: reverse the 6.0.0 to 7.0.0 merger bump in refactor(L1): merge SuperchainConfig into SystemConfig #432 while preserving the patch increment and smart-account behavior from chore: improve smart account handling #447. Regenerate semver hashes from fresh source builds rather than restoring stale hashes.
• This is a source backport, not a live migration procedure for deployments already using the merged SystemConfig. No deployment or merge is requested.

How has it been tested?

• Restored existing behavioral tests rather than adding duplicate coverage. Focused pause/SystemConfig/deployment/affected-contract tests: 442 passed, 0 failed.
• just test: 1237 passed, 0 failed, 1 skipped. forge test --match-test test_cannotReinitialize_succeeds: 2 passed.
• just lint-check, just validate-spacers-no-build, forced source builds, just snapshots, just semver-lock, and just snapshots-check-no-build pass. Regeneration leaves the committed snapshots unchanged; whitespace checks pass.
• Git comparisons confirm the changed-path set exactly matches the 54 paths from refactor(L1): merge SuperchainConfig into SystemConfig #432, nonoverlapping reverted files match its parent, and unrelated later files/semver entries remain unchanged. Overlapping portal/setup changes retain later release behavior.
• Optional just lint-forge-tests-check-no-build and fresh-source just interfaces-check-no-build retain 21 and 18 historical findings, respectively. Offending first-party sources, missing interfaces, and tool/dependency pins were checked against the parent of refactor(L1): merge SuperchainConfig into SystemConfig #432. These baseline naming/interface repairs are outside this revert.
• Forked live-upgrade tests were not run.

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