[release/11.0] Backport: named query filter set by convention cannot be overridden by explicit configuration

[Copilot]

EntityTypeBuilder.HasQueryFilter(string, LambdaExpression) created a QueryFilter without a ConfigurationSource, leaving it null. When competing against a convention-set filter (ConfigurationSource.Convention), the null source lost the override check — silently discarding the explicit user filter.

Changes

• EntityTypeBuilder.cs: Pass ConfigurationSource.Explicit in HasQueryFilter(string, LambdaExpression), matching the behavior of the unnamed overload
• InternalEntityTypeBuilderTest.cs: Add Can_override_named_query_filter_from_convention_with_explicit_configuration test

// In a convention:
builder.HasQueryFilter("filter", e => e.TenantId == tenantId); // ConfigurationSource.Convention

// In OnModelCreating — previously silently ignored, now correctly overrides:
modelBuilder.Entity<Order>().HasQueryFilter("filter", e => !e.IsDeleted);

Backport of #37710 / #37738 to release/11.0-preview2.

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