Avoid redundant type inspection and contribution during repository AOT processing

[snuderl]

Closes #3518.

Repository AOT processing walks the same domain type graph repeatedly, which makes SpringApplicationAotProcessor scale poorly with the number of repositories and the size of the domain model:

• DefaultAotRepositoryContext.discoverTypes() scans the configured base packages for types carrying the store's identifying annotations and inspects all of them — for every repository.
• TypeContributor.contribute(…) hands each resolved type to BindingReflectionHintsRegistrar individually. The registrar starts with a fresh seen set per call, so shared types are re-traversed once per resolved type.
• TypeCollector.ReachableTypes uses a per-root inspection cache, re-inspecting types reachable from more than one root.

This PR addresses all three:

• Base package scan results are cached across the repository contexts created by a RepositoryRegistrationAotProcessor.
• Reachable type inspection shares one inspection cache across all roots of a ReachableTypes instance.
• Resolved types are contributed in a single BindingReflectionHintsRegistrar pass, skipping types already contributed to the same RuntimeHints.

The generated reachability-metadata.json is unchanged. For a real application with 17 Mongo repositories over a Jackson-annotated protobuf domain model, SpringApplicationAotProcessor drops from 60s to 12s; for a synthetic application with 32 repositories, from 33.6s to 4.5s.

A standalone reproducer with scaling measurements is available at https://github.com/snuderl/spring-data-aot-repro.

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