CSHARP-5973: Support SkipWhile/TakeWhile index overloads in LINQ provider

[adelinowona]

No description provided.

[Copilot]

Pull request overview

Adds LINQ3 provider support for the indexed predicate overloads of SkipWhile/TakeWhile by translating them to $reduce with arrayIndexAs, and introduces tests/feature gating to validate behavior and server compatibility.

Changes:

• Extend method reflection metadata to recognize SkipWhile((x, i) => ...) / TakeWhile((x, i) => ...) for both Enumerable and Queryable.
• Update the SkipWhile/TakeWhile aggregation-expression translator and serializer deduction logic to handle the index parameter and emit $reduce: { arrayIndexAs: ... }.
• Add translator, serializer-finder, and integration tests, plus a new Feature.ReduceArrayIndexAs gate for integration coverage.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/SkipWhileOrTakeWhileMethodToAggregationExpressionTranslatorTests.cs	Adds AST-level unit tests for both non-indexed and indexed SkipWhile/TakeWhile translations.
tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/SerializerFinders/EnumerableTests.cs	Verifies serializer-finder resolves serializers for the new indexed overloads.
tests/MongoDB.Driver.Tests/Linq/Integration/SkipWhileOrTakeWhileWithIndexTests.cs	Adds end-to-end integration tests for indexed overloads (gated on server feature support).
src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MethodTranslators/SkipWhileOrTakeWhileMethodToAggreggationExpressoinTranslator.cs	Implements index-parameter handling and passes arrayIndexAs through to $reduce.
src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/ExpressionToAggregationExpressionTranslator.cs	Generalizes TranslateLambdaBody to accept multiple parameter symbols (needed for indexed lambdas).
src/MongoDB.Driver/Linq/Linq3Implementation/SerializerFinders/SerializerFinderVisitMethodCall.cs	Ensures the index parameter has an Int32Serializer when deducing serializers for indexed overloads.
src/MongoDB.Driver/Linq/Linq3Implementation/Reflection/QueryableMethod.cs	Adds Queryable.SkipWhile/TakeWhile MethodInfo for indexed predicate overloads.
src/MongoDB.Driver/Linq/Linq3Implementation/Reflection/EnumerableOrQueryableMethod.cs	Adds method sets for indexed overloads and includes them in relevant groupings.
src/MongoDB.Driver/Linq/Linq3Implementation/Reflection/EnumerableMethod.cs	Adds Enumerable.SkipWhile/TakeWhile MethodInfo for indexed predicate overloads.
src/MongoDB.Driver/Linq/Linq3Implementation/Ast/Visitors/AstNodeVisitor.cs	Updates reduce visitor to preserve the new ArrayIndexAs child node.
src/MongoDB.Driver/Linq/Linq3Implementation/Ast/Expressions/AstReduceExpression.cs	Adds ArrayIndexAs support to $reduce AST node rendering and updating.
src/MongoDB.Driver/Linq/Linq3Implementation/Ast/Expressions/AstExpression.cs	Extends AstExpression.Reduce factory to accept arrayIndexAs.
src/MongoDB.Driver/Core/Misc/Feature.cs	Introduces Feature.ReduceArrayIndexAs used to gate integration tests.

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[BorisDog]

LGTM + minor comment.
Also need a 2nd review from someone with LINQ expertise.

[BorisDog]

Let's have a test somewhere that uses both item and i in the expression itself, like you did in Enumerable_Select_with_index_should_work

[adelinowona]

Done