Migration to Swift

[YuriyVelichkoOpenX]

Motivation

The public classes of the Rendering Module were migrated from Objective-C to Swift. All others are on Objective-C still.

Swift Package Manager does not support mixed frameworks. Therefore we can't provide Prebbid Mobile with rendering through SPM.

We could split Objective-C and Swift parts to introduce different modules, but it controversies our modularization strategy (#395) in part dedicated to following the principles of layered architecture. So it is better to concentrate efforts on the complete migration.

Given

In the following doc, you can find the list of classes for migration

https://docs.google.com/spreadsheets/d/1ZZoRkXsIa95RZELCoEsP4IHJ5TDyRsNAlfKSQU2YohI/edit?usp=sharing

Objective

Feel free to take any Objective-C class, mark the row in the doc with yellow color, and migrate it to Swift.

Try to follow the priority column. It will help to take the less coupled classes first.

Mark migrated classes green after migration.

[YuriyVelichkoPI]

The implementation of this epic will fix SPM integration

[jsligh]

#961 should solve this issue.