Publish draft docs on draft-docs

Take care that built books are published on docs-draft.

The checkbuild tox gates copy the files to the git top-level
directory publish-docs and those can then be copied over to
docs-draft.

The patch consists of:
* A new publisher 'upload-docs-draft' for publishing the jobs
* A new publisher 'upload-doc-build-results' for publishing the log
  files of built manuals
* A new job-template 'gate-{name}-tox-doc-publish-{envlist}' that includes
  the new publishers
* Using the job-template in the docs job-group
* Update for Zuul for the above changes

blueprint draft-docs-on-docs-draft

Change-Id: Id3e9543fc67ca28e2882fb73f169d82aaec1aeb7
Merge "Publish draft docs on draft-docs"