Remove serverless related imaged from TPI registry

[kwiatekus]

Description

Use image syncer to synchronise kaniko and registry images and use synced images in serverless module.
(Alternatively: Migrate tpi image builds jobs from prow to Image Builder based GH workflow in serverless repository )

AC

• remove kaniko and registry images from third party images registry
• 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

[a-thaler]

Few components in the repo are already migrated, you can simply adopt the workflows located at https://github.com/kyma-project/third-party-images/tree/main/.github/workflows