Handle Dependency on "combined_image_styles"

Problem/Motivation

The module has a critical dependency on "Combined Image Styles", which doesn't have a stable release. This means "RIFT" can't really have a stable release until "Combined Image Styles have a stable release.

Proposed resolution

Check with the maintainer of "Combined Image Style" to see what needs to be done for it to have a stable release.

Until then, since we need only the core functionality of "combined_image_style", we can adopt those functionality into "RIFT", and later remove them when "combined_image_style" has a stable release.

Remaining tasks

- Code needs to be refactored without any breaking change to avoid dependency on combined_image_style

User interface changes

N/A

API changes

N/A

Data model changes

N/A