[Enhancement] Cache Schema instances for classes in a weak reference cache since creating an instance could be CPU intensive

[walkinggo]

Main Issue: #23707

Motivation

Cache Schema instances for classes in a weak reference cache since creating an instance could be CPU intensive

Modifications

• Added weak reference cache for schema

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[github-actions]

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[lhotari]

The implementation approach isn't correct. The cache should be an implementation details of the PulsarClientImplementationBindingImpl and not exposed externally.
The key in the cache could be the org.apache.pulsar.client.impl.schema.SchemaDefinitionImpl, however that would require adding hashCode&equals implementations to that class. The cache should have weak keys to prevent memory leaks.

[lhotari]

The cache should be encapsulated in the PulsarClientImplementationBindingImpl and not exposed outside of the interface.

[lhotari]

There's another PR #23808 where I've provided suggestions about the minimal implementation: #23808 (comment)