feat: combine image and tag in single field

[strophy]

Combines image and tag in single field, as requested here.

Issue being fixed or feature implemented

Tags are optional and do not follow any firm convention, making them hard to validate. This commit changes internal handling of tags to align with how Docker does things.

What was done?

• Merged all image/version fields into single field.

How Has This Been Tested?

• Tested create config from systemConfigs, get/set values and other commands that trigger config validation
• Tested start/status/stop/reset commands on testnet and evonet.

Breaking Changes

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[shumkov]

LGTM! 👍