Delegate immutable DataSourceMetadata to ColumnMetadata instead of snapshotting it

[xiangfu0]

What

ImmutableDataSource.ImmutableDataSourceMetadata copied ten fields out of ColumnMetadata into a per-column snapshot, about 56 bytes each. It now holds a single ColumnMetadata reference and delegates, which keeps the semantics identical because ColumnMetadata is immutable after construction: getNumDocs -> getTotalDocs, getNumValues -> getTotalNumberOfEntries, and getMaxNumValuesPerMVEntry preserves the -1 contract for single-value columns. ImmutableMapDataSource gets the same treatment, keeping its unconditional isSorted() == false and its getMaxRowLengthInBytes override.

DataSourceMetadata is never serialized and no public signature changes.

Tests

New ImmutableDataSourceTest and ImmutableMapDataSourceTest: every DataSourceMetadata getter equals the corresponding ColumnMetadata getter for a single-value INT column with min/max and partitions, a multi-value STRING column, and a virtual-column-style spec.

Why

A server keeps one metadata object graph per (segment, column) for as long as the segment is loaded, so on wide tables the per-column footprint decides how many segments a server can hold. Measured end to end on a 1000-column segment, this series takes the heap retained at load from 4.08 MB to 0.175 MB per segment (4,080 to 174 bytes per column), with a fully compacting collector on both sides. No on-disk format change, the /tables/{table}/segments/{segment}/metadata JSON stays byte-identical, and every public and SPI signature keeps working.

Stack

Based on #19473. Review this PR against its base for this layer's changes.

Current open chain; #19480 (lazy index-size storage) is already merged, and #19476 is absorbed into #19473.

1. Share FieldSpecs and repeated values across segment metadata loads #19473 shared FieldSpecs, canonical default-null values, and interned strings
2. Delegate immutable DataSourceMetadata to ColumnMetadata instead of snapshotting it #19474 delegating immutable DataSourceMetadata
3. Fold PhysicalColumnIndexContainer's IndexTypeMap into a presence mask and a dense reader array #19475 presence-mask index container
4. Materialize immutable-segment columns lazily behind an opt-in instance config (default off) #19477 opt-in lazy column materialization
5. Slim ColumnMetadataImpl to 72 bytes and derive the per-segment Schema lazily #19478 slim ColumnMetadataImpl and lazy per-segment Schema
6. Store numeric column min/max as primitives instead of boxed Comparables #19479 primitive numeric min/max
7. Hold segment column metadata in sorted arrays and derive the map on demand #19481 sorted-array column metadata storage
8. Stop the segment preprocess from building a Schema per segment #19486 segment preprocessing without building a Schema
9. Prune segments from column metadata instead of materializing them #19511 segment pruning directly from column metadata

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 67.71%. Comparing base (e265da9) to head (caac249).

Files with missing lines	Patch %	Lines
...ocal/segment/index/map/ImmutableMapDataSource.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                           Coverage Diff                           @@
##             xiangfu0/data-3221-2-intern-parse   #19474      +/-   ##
=======================================================================
+ Coverage                                57.80%   67.71%   +9.91%     
- Complexity                                   1     1450    +1449     
=======================================================================
  Files                                     2688     3490     +802     
  Lines                                   164376   225025   +60649     
  Branches                                 26688    35529    +8841     
=======================================================================
+ Hits                                     95023   152384   +57361     
+ Misses                                   61319    60614     -705     
- Partials                                  8034    12027    +3993     

Flag	Coverage Δ
integration	100.00% <ø> (+100.00%)	⬆️
integration1	100.00% <ø> (?)
integration2	0.00% <ø> (ø)
java-25	67.71% <95.23%> (+9.91%)	⬆️
lane-a	100.00% <ø> (+100.00%)	⬆️
lane-b	0.00% <ø> (ø)
temurin	67.71% <95.23%> (+9.91%)	⬆️
unittests	67.71% <95.23%> (+9.90%)	⬆️
unittests1	57.82% <47.61%> (+0.01%)	⬆️
unittests2	39.49% <95.23%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.