Add Tencent Cloud COS (cosn://, cos://) FileIO support via fsspec

### Feature Request / Improvement

Add support for [Tencent Cloud Object Storage (COS)] as a storage backend for PyIceberg, using the fsspec-compatible [cosfs](https://github.com/tencentyun/cosfs) library. This enables reading and writing Iceberg tables stored on COS via cosn:// and cos:// URI schemes

No files or tests are named in the issue. Start by locating PyIceberg’s existing fsspec-compatible FileIO entry point and review cosfs support for the cosn:// and cos:// schemes; done means Iceberg tables can be read from and written to Tencent Cloud COS through both URI forms.

Written by the indexing model from the issue text.