Split concreate and abstract dependencies

Split concreate and abstract dependencies

It adds 2 upper-constraints to pin all the dependencies.
It modifies a little bit the official upper-constraints.txt from
OpenStack due to Sphinx (4.2.0 as asked by lfdocs-conf vs 3.5.2) and
due to setuptools (58.1.0 as used in ONAP gates vs 54.1.1).

In a long run, etc/upper-constraints.os.txt should be removed once ONAP
is synced with OpenStack. For it's part, etc/upper-constraints.onap.txt
should be centralized for all ONAP projects and then removed from this
particular project.

It should be noted that lfdocs-conf still mismatches concrete and
abstract deps.

Issue-ID: DOC-765

Change-Id: Iccf1e4cdab93acc9c55acb16cb11e3b3fcef3291
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>