Cache tables are not verified as part of the health checks

The endpoints at `/api/v1/health/` and `/api/v1/health/readiness` use django-health-check in order to verify that the migrations have been run correctly. This means that the application will fail to start if the django ORM migrations have not been run. This does not happen for the cache tables.

In the case that the `createcachetable` command fails on the initial deployment, and there is no action taken based on the failed migration container, the application will still start successfully, but might fail in certain scenarios later down the line (for example cloning an environment when the application looks to clean the environments cache).

In order to resolve this, we should validate that the cache tables are created successfully as part of the readiness checks.