readfile: support `float16` data type via gdal (#1483)

* Add support for float16 data type in `readfile.py`, because for GDAL >= 3.11 you will run into `Key 15` error when trying to read float16 format files

* writefile.write(): add float16 in the supported data types

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Co-authored-by: Zhang Yunjun <yunjunz@outlook.com>