Require Optim 2 in root tests

[ChrisRackauckas-Claude]

Summary

Ignore this PR until it has been reviewed by @ChrisRackauckas.

• require Optim 2 for the Optimization root test target
• align the root test compat with the in-tree OptimizationOptimJL package, which already requires Optim 2

The root currently permits Optim 1.7.6 while its local OptimizationOptimJL source requires Optim 2. A minimum-version resolution can therefore select a root test dependency that is incompatible with the package actually under test.

Local validation

• Exact downgrade resolution on Julia 1.10 selected Optim 2.0.0 and DiffEqFlux 4.0.0.
• Locked exact-floor GROUP=Core on Julia 1.10: passed (110 utility, 22 verbosity, 1 native optimization, 2 mini-batching, 14 interface, and 18 sense-handling assertions; 1 pre-existing broken mini-batching assertion).
• Current-resolution GROUP=Core on Julia 1.12: passed (110 utility, 22 verbosity, 1 native optimization, 2 mini-batching, 14 interface, and 18 sense-handling assertions; 1 pre-existing broken mini-batching assertion).
• Current-resolution GROUP=QA on Julia 1.12: passed (18 passed, 1 pre-existing broken check).
• Runic.main(["--check", "."]): passed.
• git diff --check: passed.

[ChrisRackauckas-Claude]

Scratchpad update for commit aa577261d:

• Kept the change to the single root Optim test-compat line.
• Verified the exact Julia 1.10 graph selects Optim 2.0.0, DiffEqFlux 4.0.0, and LoggingExtras 1.1.0.
• Ran the locked exact-floor Core suite successfully: 110 utility, 22 verbosity, 1 native optimization, 2 mini-batching, 14 interface, and 18 sense-handling assertions passed; the existing mini-batching broken assertion remained reported.
• Ran fresh current Julia 1.12 Core successfully with the same group counts.
• Ran current Julia 1.12 QA successfully (18 passed, 1 pre-existing broken check).
• Runic and git diff --check pass.

This is the prerequisite for the separate LoggingExtras 1 cleanup; no additional changes are planned here.