feat: contrib Delta Change Data Feed native reads [Delta contrib split, part 5] - #9

…t, part 5]

Part 5 of the Delta Lake contrib PR breakup (tracking: apache#4366). Native Change Data Feed
(`readChangeFeed`) reads. A `RowDataSourceScanExec` over Delta's `DeltaCDFRelation` is read
natively via delta-kernel's `TableChanges` instead of vanilla Spark. The Rust `TableChanges`
path landed in parts 3a/3b; this wires the JVM side, which earlier units deferred:

- `CometDeltaCdfScanExec.scala` (new) — the CDF exec. Splits the inclusive version range into N
  partitions (one `TableChanges` sub-range each, capped by COMET_DELTA_CDF_MAX_PARTITIONS).
  Implements `CometScanWithPlanData` so the parent native block's findAllPlanData collects its
  per-partition sub-ranges (DeltaPlanDataInjector splices them) -- without that, every partition
  read the full feed and rows duplicated N-fold under an `orderBy`.
- `CometDeltaNativeScan.convertCdf` — re-added the serde method that builds the CDF scan (deferred
  from part 4b). Does not reference `ScanImpl` (lives in DeltaScanMetadata) or the orphaned
  UTF8String/DateTimeUtils imports.
- `DeltaIntegration` — re-added the CDF members (`isCdfRelation`, `transformCdf`, cached
  `convertCdfBinding`) deferred from part 4a's review, inserted before the (untouched) cached
  `scanHandler`.
- `CometExecRule` — re-added the CDF hook `case` arm deferred from part 2, after the marker hook.

All core CDF members are inert on default builds (reflective lookups of the absent contrib serde
return None -> vanilla Spark CDF read). Verified on Scala 2.12 (Spark 3.4) as well as 2.13.

Tests: CometDeltaCdcSuite (3, incl. the orderBy + unix_timestamp case that is the red-green for the
N-fold dup) and CometDeltaCdfReflectionReproSuite (3) -- all pass.

Verification: gated JVM test-compile, Scala-2.12 core compile, 6 CDF tests, spotless/scalastyle,
check-suites, gate-verify (default build still 0 Delta symbols, only the DeltaIntegration bridge).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>