Remove per-query generation of built-in record type constructors

[GuntherRademacher]

This PR removes the per-query generation of built-in record type constructors in QueryParser. Instead, constructors for built-in record types are now registered once as standard functions via the Function enum.

The constructor signatures and parameter types are still derived from the Records enum (i.e., RecordType remains the single source of truth). A new Function(RecordType) constructor and corresponding helper methods in RecordType are used to generate:

• the function signature string (e.g., name(a,b[,c])), and
• the constructor parameter types (in declaration order).

At runtime, the constructor implementation creates either:

• an XQRecordMap (for record types without optional fields), or
• a regular XQMap (if optional fields are present).

This change eliminates the repeated initialization overhead per query execution while preserving existing semantics.

There is now some similarity between RecordType.constructor() and CRecord. I did not reuse CRecord, as the Function infrastructure requires a StandardFunc. However, CRecord could potentially be refactored to build upon RecordType.constructor(). I’m submitting this early as I’ll be unavailable for the next few days, but I’m happy to follow up on the CRecord refactoring afterwards.

[ChristianGruen]

Thanks, looks fine.

However, CRecord could potentially be refactored to build upon RecordType.constructor().

I agree this sounds promising.