Reuse IcebergPageSourceProvider across splits for a scan in Lakehouse

[raunaqmorarka]

Description

This is necessary to reuse equality deletes in an iceberg scan across splits in a worker

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## Lakehouse
* Improved performance and memory usage when [Equality Delete](https://iceberg.apache.org/spec/#equality-delete-files) files are used ({issue}`28507`)

[Copilot]

Pull request overview

This PR updates the Lakehouse connector’s ConnectorPageSourceProviderFactory to reuse a single Iceberg page source provider instance across splits within the same scan, enabling reuse of equality delete state (and associated performance/memory improvements) during Iceberg reads.

Changes:

• Wrap createPageSourceProvider() with a stateful ConnectorPageSourceProvider that caches the chosen delegate provider.
• Reuse the same Iceberg page source provider across multiple createPageSource calls (splits) to allow equality delete reuse.
• Add getMemoryUsage() delegation with a 0 value before any page source is created.

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[Copilot]

Pull request overview

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