Add way to specify custom prefix for partitioned file outputs

### Is your feature request related to a problem or challenge?

Currently there is no way to control file name for generated files when you write partitioned outputs

### Describe the solution you'd like

I would like to have option to allow user to specify prefix which would allow user to have predictable part of file name instead of just randomised or `part-X`

### Describe alternatives you've considered

A more complex solution would be to introduce function callback that would be called to generate such prefix which would enable user to customise behaviour of prefix generation or replace randomized generation with his own implementation

### Additional context

_No response_

Start by locating the partitioned file output implementation and the tests covering generated file names. Trace how the current randomized or `part-X` names are produced, then define where a user-specified prefix belongs in the public interface. Done means partitioned outputs use the requested predictable prefix without breaking existing naming behavior.

Written by the indexing model from the issue text.