Support custom schemas in native sidecar function registry

[tdcmeehan]

Expected Behavior or Use Case

The native sidecar function registry should support registering functions under different catalogs and schemas, not just the built-in namespace. This would allow users to namespace their custom C++ functions separately from built-in functions, as one can do right now with a function namespace manager.

Presto Component, Service, or Connector

Native sidecar and plugin

Possible Implementation

1. Add catalog-filtered endpoint in C++: Implement a new endpoint /v1/functions/{catalog} in PrestoServer.cpp that filters functions by catalog, similar to the specification already defined in the OpenAPI spec.

2. Support multiple namespace registrations: Allow multiple native sidecar endpoints to be registered with different (non-built-in) namespaces. This capability may already be working without issue, but this requires verification.

3. Modify native sidecar plugin: Update the plugin to properly filter functions by catalog when fetching from the sidecar. Currently, all functions are bundled together regardless of catalog, which is incorrect.

Example Screenshots (if appropriate):

N/A

Context

To reach feature parity with Java, we need the ability to separately namespace functions.

[prestodb-ci]

@libianoss imported this issue as lakehouse/presto #25429