Simplified `Blubber` client to handle only the transcompilation of Blubber
configuration into Dockerfile and not the actual building of images.
Building was moved into `PipelineRunner` where all other Docker commands
are invoked.

Blubber client was refactored to use the WMF production deployment of
Blubberoid instead of relying on a locally installed binary of the
`blubber` CLI.

Bug: T212247
Change-Id: Ib403786af7af6ce9d469798452da512fa535f2b4

Will run on the experimental pipeline once
Ibb96d3ed7e9434fccc95348a8c43496f5c0b405b is deployed.

Change-Id: I91b9d82570df3cc587254f6e5b9cd531ba9b4ce0