Fix struct type metadata preservation in query results and continuations

[arnaud-lacurie]

This commit implements a solution for GitHub issue #3743 where struct type
metadata (type names like "STRUCT_1", "STRUCT_2") was getting lost during
query execution, especially in continuations.

Problem:
When executing queries that return struct types, ResultSetMetaData would return
UUID-based names (like "id...") instead of proper struct type names. This affected:

• Star expansion queries (SELECT * FROM table)
• Nested star queries (SELECT (*) FROM table)
• Direct struct projections (SELECT struct_column FROM table)
• Query continuations (EXECUTE CONTINUATION)

Root Cause:

1. Semantic analysis produces correct DataTypes with struct names ("STRUCT_1", etc.)
2. Cascades planner Type.Record loses struct names during optimization (becomes null)
3. executePhysicalPlan() previously relied only on planner types → UUID generation
4. Continuations had no semantic type info → always generated UUIDs

Solution - Hybrid Approach:

Merge semantic type structure with planner field names:

• Field names from planner Type.Record (handles aliases, star expansion, "_0" naming)
• Type structure from semantic DataTypes (preserves "STRUCT_1", "STRUCT_2")
• Additional enrichment from RecordMetaData descriptors for nested types