Enhance the use of tox

Registered by Itxaka Serrano

Summary
=======
Enhance and take advantage of tox to run our text and extra commands instead of using run_test.sh

Motivation
========
Other openstack projects use tox only for running test, setting up their environment, extracting messages and so on and we should do the same. Also using tox allows us more flexibility, less code to maintain and extra features that we dont need to implement ourselves.

Description
=========
Rework tox.ini and setup.cfg to use tox commands and environments separated from run_tests.sh

UX
===
N/A

Testing
======
We need to be careful as to make sure that all the tests are run as before as we change the tox configuration, we could be skipping tests.

Outside Dependencies
==================
No outside dependencies

Requirements Update Required
========================
No requirements

Doc Impact
=========
Should mention the deprecation of run_tests.sh on the developer documents and show some examples on how to do the same but with tox instead.

Blueprint information

Status:
Complete
Approver:
Rob Cresswell
Priority:
High
Drafter:
Itxaka Serrano
Direction:
Approved
Assignee:
None
Definition:
Approved
Series goal:
Accepted for 11.0.0-ocata
Implementation:
Implemented
Milestone target:
milestone icon ocata-2
Started by
Rob Cresswell
Completed by
Rob Cresswell

Related branches

Sprints

Whiteboard

Gerrit topic: https://review.openstack.org/#q,topic:bp/enhance-tox,n,z

Addressed by: https://review.openstack.org/259013 -- MERGED
    Enhances tox to not rely on run_tests

Addressed by: https://review.openstack.org/279189 -- ABANDONED
    [wip] experimental i9n failure on new tox.ini

Addressed by: https://review.openstack.org/318591
    Do not import local/enabled when to run test

Addressed by: https://review.openstack.org/322016
    Enable tox to run the subset test cases.

Gerrit topic: https://review.openstack.org/#q,topic:bug/1534030,n,z

Addressed by: https://review.openstack.org/325861
    Add debug envrioment into tox

Addressed by: https://review.openstack.org/381844
    Add deprecation message to run_tests.sh

Addressed by: https://review.openstack.org/391506
    Refactor tox to reduce duplication

Addressed by: https://review.openstack.org/391891
    Update the docs to remove run_tests references

Gerrit topic: https://review.openstack.org/#q,topic:bug/1638672,n,z

Gerrit topic: https://review.openstack.org/#q,topic:remove_run_tests,n,z

(?)

Work Items

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