feat: vortex-datafusion segment cache

[ch-sc]

Summary

vortex-layout already provides a SegmentCache trait and a MokaSegmentCache implementation, and vortex-file's OpenOptions already has with_segment_cache() that wires it into every file open. vortex-datafusion just did not thread this through and so every new query re-reads data segments.

This PR:

• Adds segment_cache: Option<Arc<dyn SegmentCache>> to VortexOpener and VortexSource.
• Passes the cache into OpenOptions::with_segment_cache() when opening each file in VortexOpener::open().
• Exposes VortexSource::with_segment_cache() so callers can inject a shared cache instance.

Closes: #000

API Changes

 impl VortexSource {
      /// Sets a [`SegmentCache`] to reuse decoded segment bytes across scans of the same file.
      pub fn with_segment_cache(self, segment_cache: Arc<dyn SegmentCache>) -> Self;
  }

Testing

The segment_cache field defaults to None, so all existing behavior is unchanged when the cache is not configured.

[AdamGS]

I think there's an issue here where that the segment caches uses SegmentId for its keys, so you can't be re-used across files as they are not unique IIRC.
In some cases this will probably work correctly, but often a single VortexSource will be shared between multiple files.

[ch-sc]

Ah, I see. SegmentId is file dependent, but only consists of a u32.

I don't have a clear solution in mind, but if SegmentId would contain file information (maybe path and an e-tag for updates to the file) we could resolve the file dependency.