Remove Nuget repo model and flatten RemoteRepository model

[moss-n]

Description

This change flattens the RemoteRepository model and removes the Nuget repository model. The attributes of the Nuget repository have been moved to the RemoteRepository model. When JSON encoded, this model is in a structure that is expected by the Artifactory API when making calls to create/update a RemoteRepository of type NuGet.

Fixes #106

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

How has it been tested ?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• [x] Pre-Commit
• [x] pytest --cov=pyartifactory --cov-branch

Checklist:

• [x] My PR is ready for prime time! Otherwise use the "Draft PR" feature
• [x] All commits have a correct title
• [ ] Readme has been updated
• [x] Quality tests are green (see Codacy)
• [ ] Automated tests are green (see pipeline)