Find a record's synthesized members through IRecordFacet, not by name #222

Goal

Replace the name-based lookup of a record's synthesized members in the aspects with Metalama 2027.0's record facet. Needs #173.

ValueObjectDeclaration.cs finds a hand-written PrintMembers by name (method is { Name: "PrintMembers", ... }, around line 389). Metalama 2027.0 adds INamedType.Facets, where IRecordFacet exposes the members the compiler synthesizes for a record: EqualityContract, PrintMembers, the copy constructor and Deconstruct (release notes, "Type facets").

To measure

• Whether the facet identifies a user-declared PrintMembers, which replaces the synthesized one, or only the synthesized members. If it can't tell them apart, the name lookup stays and this closes as not planned.
• Any other lookup of a record member by name in src/CodoMetis.TypeKit.Generators (git grep for the names above), handled the same way.

Done when

The same answers on the existing tests over the record shapes of the generated-type axes, with the lookup going through the facet. This is a refactor with no behaviour change, shown by a seeded hand-written PrintMembers in a base record still being reported.