Add V7 raw forward index format for codec pipelines

[xiangfu0]

Summary

• Adds a self-describing V7 fixed-byte forward-index format with explicit magic and the canonical codecSpec in its header.
• Routes every non-null codecSpec, including plain LZ4, SNAPPY, GZIP, and ZSTD, through V7. Legacy compression configuration still selects legacy formats.
• Fails table-config validation unless codec pipelines target an enabled RAW, single-value INT/LONG forward index with a valid pipeline and bounded V7 chunk settings.
• Reconciles legacy-to-V7, V7 spec changes, unchanged V7, and V7-to-legacy transitions during reload.
• Preserves the historical reader path for old fixed-byte versions, including legacy version 7, unless the new discriminator is present.

Compatibility

This is an on-disk upgrade boundary. Upgrade every component that may build or read segments before enabling codecSpec. Before a binary rollback, remove codecSpec and reload or regenerate affected V7 forward indexes into a legacy format.

Verification

• Real codec round trips, corrupt-input cases, released legacy fixtures, factory routing, table validation, and reload transitions.
• Real offline and realtime clusters with no mocks, both query engines, Kafka force-commit/load, and direct V7 reader verification.
• Spotless, Checkstyle, license formatting, and license checks on all affected modules.

Stack

#19306 is merged. This PR now owns V7 selection, validation, reload reconciliation, and end-to-end coverage. Child PRs #19308 and #19309 need to be rebased parent-first with duplicated behavior removed.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 4.82574% with 355 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.52%. Comparing base (5e914c9) to head (00bceb0).

Files with missing lines	Patch %	Lines
.../forward/FixedByteChunkSVForwardIndexReaderV7.java	0.00%	145 Missing and 1 partial ⚠️
...riter/impl/FixedByteChunkForwardIndexWriterV7.java	0.00%	143 Missing ⚠️
.../local/segment/index/forward/ForwardIndexType.java	4.54%	20 Missing and 1 partial ⚠️
.../impl/fwd/SingleValueFixedByteRawIndexCreator.java	0.00%	10 Missing ⚠️
...ment/index/forward/ForwardIndexCreatorFactory.java	28.57%	5 Missing and 5 partials ⚠️
...ocal/segment/index/loader/ForwardIndexHandler.java	37.50%	5 Missing and 5 partials ⚠️
...ment/index/readers/forward/ChunkReaderContext.java	0.00%	7 Missing and 1 partial ⚠️
...gment/index/forward/ForwardIndexReaderFactory.java	46.15%	5 Missing and 2 partials ⚠️

❗ There is a different number of reports uploaded between BASE (5e914c9) and HEAD (00bceb0). Click for more details.

HEAD has 4 uploads less than BASE

Flag	BASE (5e914c9)	HEAD (00bceb0)
unittests	2	1
java-25	6	5
temurin	6	5
unittests2	1	0

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #19307       +/-   ##
=============================================
- Coverage     67.55%   57.52%   -10.03%     
+ Complexity     1430        7     -1423     
=============================================
  Files          3486     2688      -798     
  Lines        224100   164280    -59820     
  Branches      35370    26674     -8696     
=============================================
- Hits         151392    94505    -56887     
- Misses        60678    61758     +1080     
+ Partials      12030     8017     -4013     

Flag	Coverage Δ
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-25	57.52% <4.82%> (-10.03%)	⬇️
lane-a	100.00% <ø> (ø)
lane-b	0.00% <ø> (ø)
temurin	57.52% <4.82%> (-10.03%)	⬇️
unittests	57.52% <4.82%> (-10.03%)	⬇️
unittests1	57.52% <4.82%> (-0.12%)	⬇️
unittests2	?

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