Clean up the base code for crystal

[skdwriting]

Issue/Feature Description:
As we have moved metadata management base code from strato to crystal project, there are unwanted files or references. This needs clean up

• multicloud references
• unwanted backend files
  Examples:
  (https://github.com/sodafoundation/crystal/tree/main/backend/pkg/utils/constants)
  /constants.go
  There are references to backends which are not relevant etc.

Basically we need to have a code review, identify issues and track to closure
Why this issue to fixed / feature is needed(give scenarios or use cases):
Unwanted

How to reproduce, in case of a bug:
NA

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)