feat: Add synology file station support

It seems interesting to add [synology file station](https://www.synology.com/en-global/dsm/overview/file) support in OpenDAL so users with synology can use applications that powered by OpenDAL to access data directly.

[API Docs](https://global.synologydownload.com/download/Document/Software/DeveloperGuide/Package/FileStation/All/enu/Synology_File_Station_API_Guide.pdf)

## Problems

### Use cases

Will users want to use this service? Maybe it's easier to mount to local and use POSIX fs directly?

### Integration tests

But synology file station is part of synology's DSM which is limited to install on synology's hardware.

I'm not sure if we can use https://github.com/kroese/virtual-dsm to perform integration tests in our CI.

Start by reading the linked Synology File Station API Guide and assessing whether its service can be integrated with OpenDAL. Investigate the referenced virtual-dsm project for a possible CI integration-test environment. Done means the feasibility questions are resolved and File Station support has a tested integration path.

Written by the indexing model from the issue text.