Revamp Tekton pipeline (#114)

* Switch to multi-arch build
* Increase memory for clamav scan
* Increase pipelinerun timeout
* Use separte pipeline run definitions in order to have separate specs
  There aren’t robust enough filters and expressions in PAC to dynamically
  set the parameters. It’s simpler to have some redundancy.

* Get version tag and apply it to the image
* Add version_tag label to image for later use
  There’s an open RFE to be able to use image labels for release tags

* Update image for build-image task
  This should fix the problem with BUILD_ARGS