Migrate from build prow jobs to the Image Builder GH Workflow

[kwiatekus]

Description

Migrate image build jobs from prow to Image Builder reusable workflow.

AC

• all images that make our kyma module should be built as part of our GH ci/cd workflows
• do not leave orphaned prow jobs - cleanup build job configs from test-infra repository
• update contributor's guides if necessary

Reasons

As we have migrated all our tests to GH workflows already, its also time to embed image build jobs into the workflows and get rid of the dependency to prow as built system and to eliminate flakiness resulting from having to use 2 systems.

Attachments

User Guide from tooling team