[GLUTEN-12597][CORE] Migrate TopNRel to Expression count + FetchMode (Substrait 0.98)

[nielspardon]

What changes are proposed in this pull request?

Substrait 0.98 redesigned TopNRel: the scalar int64 n = 3 became Expression count = 5, sorts moved to field 3, and it gained Expression offset = 4 and FetchMode mode = 6. This migrates Gluten's vendored proto, the JVM producer, and the Velox consumer/validator in lockstep, as one step of the Substrait v0.23.0 → 0.98.0 proto rebase (#12597).

Gluten's only TopNRel producer (TopNTransformer, Spark's TakeOrderedAndProject) always supplies a literal Long limit with no offset and no ties, so the producer wraps the limit into an i64-literal Expression and sets FETCH_MODE_ROWS_ONLY explicitly (FETCH_MODE_UNSPECIFIED is merely the proto3 default and not a valid producer choice). TopNRel stays at Rel-oneof field 19, so there is no oneof renumbering.

• Proto: replace int64 n = 3 / sorts = 4 / advanced_extension = 10 with the 0.98 body (sorts = 3, offset = 4, count = 5, mode = 6, advanced_extension = 7) and add the top-level FetchMode enum (vendored verbatim from 0.98).
• Producer: TopNNode wraps the limit via ExpressionBuilder.makeLongLiteral, sets FETCH_MODE_ROWS_ONLY, and now attaches RelCommon (previously it was built but never set).
• Velox: SubstraitToVeloxPlan and SubstraitToVeloxPlanValidator extract the count via a new SubstraitParser::getRowCount helper — which rejects a count that is not a positive i64 literal in [1, INT32_MAX] — and reject an offset or any mode other than FETCH_MODE_ROWS_ONLY. The converter mirrors the validator so a plan reaching it with native validation disabled (or via the JSON-plan/benchmark paths) fails loudly instead of silently dropping OFFSET / WITH TIES semantics. The validator also rejects an empty sort list, which core::TopNNode asserts against.

ClickHouse has no TopNRel parser, and the Velox → Substrait reverse converter maps a Velox TopNNode to a FetchRel (not a TopNRel), so neither is affected.

How was this patch tested?

• New TopNRelProtoSuite pins the producer contract (the count lands as an i64-literal expression, FETCH_MODE_ROWS_ONLY, no offset, RelCommon direct) and asserts the 0.98 field numbers on the descriptor (a same-schema round trip cannot catch a renumber).
• Locally verified: protoc dup-field check; gluten-substrait builds and the new suite passes (mvn -Pspark-3.5); the Velox native backend compiles and links (consumer, validator, and the new getRowCount helper); clang-format (v15) clean on all changed C++ files.
• Existing end-to-end TakeOrderedAndProject suites exercise the consumer extraction on Velox.

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[github-actions]

Run Gluten Clickhouse CI on x86

[JkSelf]

@nielspardon LGTM. Thanks for your work. Could you help to remove the TopNRel changes in SubstraitModifications.md ?

[nielspardon]

Could you help to remove the TopNRel changes in SubstraitModifications.md ?

Do you prefer to update the docs file on each PR or should do we one consolidation round at the end?

[JkSelf]

Could you help to remove the TopNRel changes in SubstraitModifications.md ?

Do you prefer to update the docs file on each PR or should do we one consolidation round at the end?

@nielspardon It is ok for me to combine these changes into single PR at the end.

[JkSelf]

LGTM. Thanks for your work