Fixes #4826 - rework reposets to not create repositories on repo set enable

The previous way of reposet enable was creating disabled repositories
when the reposet was enabled. These repositories were not usable till
enabled and it takes quite long to have them created, provided that
most of the disabled repositories will not be used anyway.

It also meant we needed to keep the repos in sync with the CDN, once
the reposet was enabled.

With the new approach, there is no notion of enabled/disabled
repository set. Instead, one can get the list of available
repositories for the repository set and enable/disable subset
of the available repositories. Enable available repository means
creation of the repository, disable means deletion. Therefore, no need
for having special flag tracking the enablement status on the
repository itself.
Fixes #5201 - allow disabling lazy accessors in tests

Makes it easier to set up the testing instances without explicitly
listing what should be disabled.
Fixes #5023 - Repository::Destroy doesn't continue when failed in ActiveRecord
Fixes #4826 - fix rubocop
Fixes #4826 - address review comments
Fixes #4924 - dynflow migration for product create

dynflow migration of product creation

unit tests for product create

removed old product create unit test
fixed other unit tests
Merge pull request #3980 from iNecas/reposets-rework

Fixes #4826 - rework reposets to not create repositories on repo set enable
Fixes #5448 - Fix a typo in the subscriptions page
Merge pull request #4007 from bkearney/bkearney/5448

Fixes #5448 - Fix a typo in the subscriptions page
fixes #5412 - adding content view deletion ui
Merge pull request #3911 from parthaa/product-create

Fixes #4924 - dynflow migration for product create
Merge pull request #4001 from jlsherrill/view_delete

fixes #5412 - adding content view deletion ui
fixes #5411 - precreating backend object search indexes
 As part of this, updated the pool object to include BackendIndexedModel
Merge pull request #4008 from jlsherrill/search_index

fixes #5411 - precreating backend object search indexes
Fixes # 5437 - Env controller cleanup

Removing unused controller methods from the environments controller.
Also wiping out unused tests.