Make imports shortcuts

[mimi030]

Amendments Overview:
 This pull request introduces the following improvements:

• Simplified import statements in the 'losses' module.
• Simplified imports from the 'miners' module.
• Simplified import paths for the 'models' module.
• Simplified import statements in the 'samplers' module.
• Simplified import examples in the 'Features Extraction' documentation.
• Simplified imports from 'losses', 'models', 'miners', and 'samplers' within the '/oml' module.
• Added dependencies installation info to contribution guide

Notes:
 By moving import statements into the corresponding modules' init.py files, most imports are simplified. A few import statements remain unchanged to prevent circular import issues.

Additionally, the import examples in the 'Features Extraction' documentation in Colab require permission to proceed, so they remain unchanged.

[AlekseySh]

Hey, @mimi030 After you solve the conflicts, we can run CI/CD

[AlekseySh]

Also, please, double check contribution pipeline & see how to update Readme

[AlekseySh]

And just to make sure we are on the same page: it's not necessary to simplify the imports inside the modules. I mean, you can do it, but the final purpose if to simplify examples, so, you can only simplify imports there.

[mimi030]

And just to make sure we are on the same page: it's not necessary to simplify the imports inside the modules. I mean, you can do it, but the final purpose if to simplify examples, so, you can only simplify imports there.

So just to clarify, should I focus only on updating the import statements in the examples found under Features Extraction? I'm feeling a bit confused about the task scope now, as I had understood from our discussion here that we were looking to implement these changes more broadly.

To ensure I'm on the right track, could you please specify which specific files I should be targeting for these updates?

Thank you for your guidance!

[mimi030]

Also, please, double check contribution pipeline & see how to update Readme

Certainly! I've previously gone through the Contributing in general and Contributing to documentation, but I'll be happy to double-check everything again to ensure everything is in order. If you have specific areas or updates you'd like me to focus on, please let me know.

[AlekseySh]

from the guide:

## Contributing to documentation
* If you want to change `README.md` you should go to `docs/readme`, change the desired section and then build
  readme via `make build_readme`. *So, don't change the main readme file directly, otherwise tests will fail.*

[AlekseySh]

Close because of: https://github.com/OML-Team/open-metric-learning/issues/535#issuecomment-2155004071