Rename LogicalType and DataChunk to have Handle suffix

[Swoorup]

More refactoring changes from #337

• Rename LogicalType and DataChunk to have Handle suffix, as these are just reference handle to the duckdb'c api's. LogicalType and DataChunk will be used later to contain more information about the themselves.
• Introduce DuckDbString as this need to be cleanup using a Duckdb C api. Mostly to wrap unsafe functions.
• Use num-integer version from root manifest toml for consistency
• Also mark functions/convert to unsafe equivalent instead of using the from trait, when getting their inner field directly from c api, to mark it as unsafe.

[Mytherin]

Thanks!