[TASK] Use component image tag instead of the global tag

[aabouzaid]

Related to

Epic: https://github.com/camunda/distribution/issues/148

Overview

Now most of the Camunda application has its own patch version and it's expected to have this for all components.

Actions

• [x] Targeted versions: 8.5 and 8.6
• [x] Set the global tag image global.image.tag to empty value.
• [x] Set the version for each component tag image e.g. zeebe.image.tag.
• [x] Ensure that Renovatebot uses the docker datasource, not the github datasource.

### Sub-tasks
- [ ] https://github.com/camunda/camunda-platform-helm/pull/2069
- [ ] https://github.com/camunda/camunda-platform-helm/pull/2080
- [ ] https://github.com/camunda/camunda-docs/pull/3999
- [x] Inform Stakeholders.

[aabouzaid]

All actions are done :heavy_check_mark:

[aabouzaid]

I reopened this task to implement the support team's suggestion and add this change to the official docs (even if it's not a breaking change to ensure it's clear for the users).

[aabouzaid]

All sub-tasks are done.