revert: Make blockstore an installable package

[kdmccormick]

Reverts #135

We noticed a spike in BundleNotFound errors from LMS shortly after that PR was released.

Example stack trace:

Nov  8 15:15:38 ip-x-x-x-x [service_variant=lms][django.request][env:prod-edx-edxapp] ERROR [ip-x-x-x-x  xxxx] [user None] [ip x.x.x.x] [log.py:224] - Internal Server Error: /api/xblock/v2/xblocks/lb:LabXchange:631f3623:video:1/handler/25274342-fbe56f2245550b55a88c/yt_video_metadata/
Traceback (most recent call last):
  File "/edx/app/edxapp/edx-platform/openedx/core/lib/blockstore_api/methods.py", line 170, in get_bundle
    data = api_request('get', api_url('bundles', str(bundle_uuid)))
  File "/edx/app/edxapp/edx-platform/openedx/core/lib/blockstore_api/methods.py", line 48, in api_request
    raise NotFound
openedx.core.lib.blockstore_api.exceptions.NotFound
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3.8/contextlib.py", line 75, in inner
    return func(*args, **kwds)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/newrelic/hooks/framework_django.py", line 562, in wrapper
    return wrapped(*args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/views/decorators/clickjacking.py", line 50, in wrapped_view
    resp = view_func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/xblock/rest_api/views.py", line 152, in xblock_handler
    block = load_block(usage_key, user)
  File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/xblock/api.py", line 76, in load_block
    if user is not None and not context_impl.can_view_block(user, usage_key):
  File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/content_libraries/library_context.py", line 72, in can_view_block
    def_key = self.definition_for_usage(usage_key)
  File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/content_libraries/library_context.py", line 96, in definition_for_usage
    return bundle.definition_for_usage(usage_key)
  File "/edx/app/edxapp/edx-platform/openedx/core/djangoapps/content_libraries/library_bundle.py", line 151, in definition_for_usage
    version_arg = {"bundle_version": get_bundle_version_number(self.bundle_uuid)}
  File "/edx/app/edxapp/edx-platform/openedx/core/djangolib/blockstore_cache.py", line 139, in get_bundle_version_number
    bundle_metadata = blockstore_api.get_bundle(bundle_uuid)
  File "/edx/app/edxapp/edx-platform/openedx/core/lib/blockstore_api/methods.py", line 172, in get_bundle
    raise BundleNotFound(f"Bundle {bundle_uuid} does not exist.")  # lint-amnesty, pylint: disable=raise-missing-from
openedx.core.lib.blockstore_api.exceptions.BundleNotFound: Bundle 7255a2cc-facd-45ac-ba96-58f0f1d4d0de does not exist.

[connorhaugh]

Looks like the revert matches, should be good to go.