Fix variable coercion for expression-based filter fields

[glen-84]

Summary

• Expression-based filter fields (for example descriptor.Field(x => x.Bars.OrderByDescending(b => b.Id).Take(1))) registered the expression's return type as the field's input coercion runtime type. When the filter was supplied through a GraphQL variable, variable coercion tried to materialize the filter value into that type and failed for non-constructible types such as collection interfaces, rejecting the request with HC0016: Variable 'where' got an invalid value.
• Expression-based filter fields now leave the coercion runtime type unset, so filter variable values materialize as plain dictionaries, exactly like member-bound filter fields. The expression's return type is still used to build the filter predicate, so filtering behavior is unchanged.

Test plan

• New Create_CollectionExpression_WithVariables snapshot test: a collection-valued expression field filtered through a variable, asserting matching and non-matching results.
• Ran the filter suites for every provider locally: Data.Filters.Tests, Data.Filters.InMemory.Tests, Data.Filters.SqlServer.Tests, MongoDb, Marten, Raven, and Spatial.

Closes #7024
Supersedes #9266

[Copilot]

Pull request overview

Fixes variable coercion failures for expression-based filter fields by avoiding registration of the expression return type as the field’s input coercion runtime type, while still preserving the expression return type for predicate construction.

Changes:

• Stop setting FilterFieldConfiguration.RuntimeType from expression return types during filter field descriptor construction to prevent variable materialization into non-constructible interface types.
• Ensure FilterField.RuntimeType is still derived from the expression return type during type completion so expression-based predicates continue to work.
• Add an in-memory snapshot test covering filtering a collection-valued expression field via GraphQL variables.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/HotChocolate/Data/test/Data.Filters.InMemory.Tests/QueryableFilterVisitorExpressionTests.cs	Adds a regression test for variable-based filtering against a collection-valued expression field.
src/HotChocolate/Data/test/Data.Filters.InMemory.Tests/snapshots/QueryableFilterVisitorExpressionTests.Create_CollectionExpression_WithVariables.snap	Snapshot for the new regression test (match + no-match cases).
src/HotChocolate/Data/src/Data/Filters/FilterFieldDescriptor.cs	Removes expression-based assignment of Configuration.RuntimeType to avoid incorrect variable coercion behavior.
src/HotChocolate/Data/src/Data/Filters/Fields/FilterField.cs	Restores runtime type derivation for expression fields at completion time to keep predicate building behavior unchanged.

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[github-actions]

Patch coverage

100.0% of changed lines covered (4/4)

File	Covered	Changed	Patch %
src/HotChocolate/Data/src/Data/Filters/Fields/FilterField.cs	4	4	100.0% 🟢

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Project coverage: 53.8% (231323/430064 lines)