Switch to newer openstackdocstheme and reno versions

Switch to openstackdocstheme 2.2.1 and reno 3.1.0 versions. Using
these versions will allow especially:
* Linking from HTML to PDF document
* Allow parallel building of documents
* Fix some rendering problems

Update Sphinx version as well.

Disable openstackdocs_auto_name to use 'project' variable as name.

Change pygments_style to 'native' since old theme version always used
'native' and the theme now respects the setting and using 'sphinx' can
lead to some strange rendering.

openstackdocstheme renames some variables, so follow the renames
before the next release removes them. A couple of variables are also
not needed anymore, remove them.

See also
http://lists.openstack.org/pipermail/openstack-discuss/2020-May/014971.html

Change-Id: Iefbde88aa089a12a34fa1243c4d626127bb2bec6

doc/requirements.txt

@@ -2,6 +2,6 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-openstackdocstheme>=2.0.0 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0
 sphinx>=2.0.0,!=2.1.0 # BSD
 yasfb>=0.5.1

doc/source/conf.py

@@ -35,9 +35,10 @@ extensions = ['sphinx.ext.autodoc',
              ]
 
 # openstackdocstheme options
-repository_name = 'openstack/cinder-specs'
-bug_project = 'cinder-specs'
-bug_tag = 'doc'
+openstackdocs_repo_name = 'openstack/cinder-specs'
+openstackdocs_auto_name = False
+openstackdocs_bug_project = 'cinder-specs'
+openstackdocs_bug_tag = 'doc'
 
 # Feed configuration for yasfb
 feed_base_url = 'http://specs.openstack.org/openstack/cinder-specs'

test-requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-openstackdocstheme>=2.0.0 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0
 sphinx>=2.0.0,!=2.1.0 # BSD
 flake8
 yasfb>=0.5.1