Giorgi/DuckDB.NET

AI Summary: This issue proposes several performance optimizations for the project, primarily suggesting a migration from `DllImport` to `LibraryImport` to reduce marshalling overhead and potentially increase throughput. Additionally, it recommends micro-optimizations such as using `string.Create` to reduce allocations in `StringVectorDataReader` and `Span<char>` for `GuidConverter` to avoid allocations when building GUID representations.