create new bulk host create endpoint

allow system admins, org admins, and inventory admins to bulk create
hosts.

Testing on an "open" licensed awx as system admin, I created 1000 hosts with 6 queries in ~ 0.15 seconds
Testing on an "open" licensed awx as organization admin, I created 1000 hosts with 11 queries in ~ 0.15 seconds

fix org max host check

also only do permission denied if license is a trial

add /api/v2/bulk to list bulk apis available

add api description templates

One motiviation to not take a list of hosts with mixed inventories is to
keep things simple re: RBAC and keeping a constant number of queries.

If there is great clamor for accepting list of hosts to insert into
arbitrary different inventories, we could probably make it happen - we'd
need to pop the inventory off of each of the hosts, run the
HostSerializer validate, then in top level BulkHostCreateSerializer
fetch all the inventories/check permissions/org host limits for those
inventories/etc. But that makes this that much more complicated.

add test for rbac access

test also helped me find a bug in a query, fixed that

add test to assert num queries scales as expected

also move other test to dedicated file

also test with super user like I meant to

record activity stream for the inventory

this records that a certain number of hosts were added by a certain user
we could consider if there is any other additional information we want
to include

awx/api/urls/urls.py

@@ -31,6 +31,10 @@ from awx.api.views import (
     ApplicationOAuth2TokenList,
     OAuth2ApplicationDetail,
 )
+from awx.api.views.bulk import (
+    BulkView,
+    BulkHostCreateView,
+)
 from awx.api.views.mesh_visualizer import MeshVisualizer
 
 from awx.api.views.metrics import MetricsView
@@ -136,6 +140,8 @@ v2_urls = [
     re_path(r'^activity_stream/', include(activity_stream_urls)),
     re_path(r'^workflow_approval_templates/', include(workflow_approval_template_urls)),
     re_path(r'^workflow_approvals/', include(workflow_approval_urls)),
+    re_path(r'^bulk/host_create/$', BulkHostCreateView.as_view(), name='bulk_host_create'),
+    re_path(r'^bulk/$', BulkView.as_view(), name='bulk'),
 ]