[Parquet reader] support reading small decimals with DBP encoding

[samansmink]

This adds support for small decimals that are encoded with DELTA_BINARY_PACKED encoding.

This encoding is only supported for int32 and int64, but in the case of the parquet file in the test here, the type, DECIMAL(1,0) translates to a int16 in duckdb triggering the DELTA_BINARY_PACKED should only be INT32 or INT64 warning.

This is incorrect because the switch statement looked at the duckdb type, not the parquet schema type.

[Mytherin]

Thanks! LGTM