Isolate OptimizationBase Enzyme tests from prerelease Core

[ChrisRackauckas-Claude]

Ignore this PR until reviewed by @ChrisRackauckas.

Summary

• Move the Enzyme-loading OptimizationBase tests into test/AD with their own project.
• Declare the sublibrary AD group for Julia lts and 1, excluding pre.
• Use SciMLTesting's group dispatcher for Core, AD, and QA environment setup.
• Remove AD-only dependencies from the OptimizationBase Core test target.

Why

The root AD suite was isolated in #1261, but lib/OptimizationBase still loaded Enzyme from its Core group, which includes Julia prereleases. This completes the test-layout fix and leaves the production OptimizationEnzymeExt.lagrangian implementation unchanged. It replaces the production workaround proposed in #1265; Enzyme's Julia 1.13 support should be fixed upstream before Julia 1.13 is released.

Validation

• Julia 1.13-rc1, OPTIMIZATION_TEST_GROUP=Core: 52/52 passed in 3m52.6s; the resolved test environment contained no Enzyme.
• Julia 1.12, OPTIMIZATION_TEST_GROUP=AD: 725/725 passed in 24m53.0s.
• Julia 1.10, OPTIMIZATION_TEST_GROUP=AD: 725/725 passed in 14m22.6s; local OptimizationBase, OptimizationLBFGSB, and OptimizationManopt paths resolved correctly.
• Julia 1.12, OPTIMIZATION_TEST_GROUP=QA: 18 passed, 1 known broken, in 1m39.8s.
• Runic checks passed for all changed and moved Julia files.
• git diff --check passed.