WL-926

This specifically enables/disables the underlying comment service client
used to make calls to the service.  When disabled, this client will now
throw an exception which can be propagated upwards so that callers can
make the right decision about how to notify users of the error, or
handle retry, etc etc.

- Default to with_responses=False, except when required.
- Clean up search call unused params.

We're often grabbing the metadata of a specific thread to then be able
to perform other operations, but we never need the actual responses or
comments of a thread unless we're displaying it in the normal forum
view.

This change sets a default of with_responses=False, which instructs the
comment service to not send back the responses/comments for the given
thread.  We only ask for responses in the case of rendering a single
thread or inline discussion.

2. Add site configuration overrides to theming/helpers.py
3. Move microsite.get_value from theming/helpers to site_configuration/helpers
4. Move microsite_configuration.microsite.get_value usages to site_configuration.helpers.values

More accurately, this creates a 4th shard because the
last shard is always the default.

TEST_DATA_MIXED_MODULESTORE
Remove these test mixed modulestores:
TEST_DATA_MIXED_TOY_MODULESTORE
TEST_DATA_MIXED_CLOSED_MODULESTORE
TEST_DATA_MIXED_GRADED_MODULESTORE

More accurately, this creates a 4th shard because the
last shard is always the default.

TEST_DATA_MIXED_MODULESTORE
Remove these test mixed modulestores:
TEST_DATA_MIXED_TOY_MODULESTORE
TEST_DATA_MIXED_CLOSED_MODULESTORE
TEST_DATA_MIXED_GRADED_MODULESTORE

It was introduced back in 2012, and is not used in the default
configuration.

There's no need to use a string literal in setattr, delattr, or the
two-argument form of getattr.

Remove filtering by partition, course and user
Rewrite the LMS result processor to use the course blocks api

These signals are caught by the Teams app and used to update
`last_activity_at` on both teams and individual users.

TNL-2497

TNL-2864

New classes for the return type, and changes to the has_access function and tests to make them compatible.

Skipped 'print' statement violations, as print() is Py3k syntax.