Support setting `image.tagSuffix` to simplify UBI image specification

Summary

Context: !2415 (comment 871043993)

Proposal: support the ability to set image.tagSuffix to simplify UBI image specification.

Example:

# Globally
global:
  image:
    tagSuffix: -ubi8

# Locally
gitlab:
  webservice:
    image:
      tagSuffix: -ubi8

Acceptance criteria

• Tag suffix can be specified globally
• Tag suffix can be specified per component/chart