Align DuckDB Excel API with SQLite and add DuckTools parity

[Dagalon]

Motivation

• Make DuckDB and SQLite Excel worksheet APIs consistent so callers can use the same signatures across engines.
• Bring DuckDB runtime helpers in line with SQLite helpers (identifier quoting, parameter naming, SQL/file resolution and table management) for parity and reuse.
• Update documentation and add a class-structure guide in English so the API alignment is discoverable for consumers.

Description

• Aligned Excel function headers and behaviors in XLS-Memory-Lib/DuckDbExcelFunctions.cs to match SQLite (e.g. MEMORY_DB.DUCKDB.CREATE_DB(name, path), TABLES(databaseId, dependency), CREATE.TABLE(databaseId, table, range, dependency), INSERT/EXECUTE/SCALAR/QUERY(..., dependency), and added DROP.TABLE).
• Added helper APIs to DuckDB-Memory-Lib/DuckTools.cs: made DuckTools partial, added QuoteIdentifier, ParameterName, ResolveSql, improved GetListTables behavior, DropTable, DeleteDataBase, and a generated-regex hook (MyRegex) to mirror SQLite helper capabilities.
• Added TABLE_NOT_FOUND to DuckDB-Memory-Lib/EnumsDuckMemory.cs so DuckDB can return the same table-drop status as SQLite.
• Documentation: updated README.md to reflect the unified Excel function signatures and added CLASS_STRUCTURE.md (Mermaid diagrams) describing package/class relationships and the aligned Excel surface.

Testing

• Attempted dotnet build MSBuild/MemoryDb-Lib.sln and dotnet test MSBuild/MemoryDb-Lib.sln but both could not be executed in this environment because dotnet is not available (automated test execution blocked).
• Ran basic repository checks (git diff --check) locally in the environment and no whitespace/patch errors were reported.

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Codex Task