Improve apply properties and methods (#3495)

- Call apply method after create method
- Annotate URL parameters of created method that are not covered by base URL
- Apply schema to properties supports list of union classes
- Apply schema to properties automatically picks type value for union classes
- Remove `super()._initAttributes` and `super()._useAttributes` from created `NonCompletableGithubObject`s
- Class names for schemas of properties of other classes are named after that other class plus the property name
- Rework default and fallback types when making union class attributes