Support appending all data types

[jraymakers]

It's not currently possible to append all data types, because the C API doesn't provide such support (as of 1.1.3). The necessary C API support is on track to ship with DuckDB 1.2; this issue tracks adding the necessary bindings and API functions to expose this functionality when it becomes available.

The following types need support:

• DECIMAL
• TIMESTAMP_S
• TIMESTAMP_MS
• TIMESTAMP_NS
• ENUM
• LIST
• STRUCT
• MAP
• ARRAY
• UUID
• UNION
• BIT
• TIME_TZ
• TIMESTAMP_TZ
• VARINT

This issue covers appending values one-by-one. Appending data chunks, which is more efficient for bulk loading, is already technically supported, although creating and writing data chunks, which is necessary for most use cases, is not. The latter is covered by #85.