Owlvit model enhancements

[probicheaux]

Description

Does a few things:

1. Adds in negative prompting per class for owlvit
2. Uses multiple examples per class by argmax, instead of meaning them
3. Refactors some of these very heavy methods

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How has this change been tested, please provide a testcase or example of how you tested the change?

Integration tests, and tested extensively via roboflow UI

Any specific deployment considerations

No

Docs

• Docs updated? What were the changes:

Much of the thought here comes from @isaacrob-roboflow and https://github.com/DirectAI/simple-data-free-model-server

[PawelPeczek-Roboflow]

@probicheaux - shall we merge?