[ticket/11305] Extract hook finder from cache service.

Unlike most other things in cache service, hook finder does not need
a database connection.

PHPBB3-11305
[ticket/11305] Retrieve cache driver from container rather than cache service.

This only covers some of the call sites.

PHPBB3-11305
[ticket/11305] Create a normal container during final installation step.

The final step calls a bunch of code which expects a full phpBB
runtime environment. Also, by this step everything should be configured
and database schema set up.

Therefore, in the final step replace installer container with a normal
phpBB container.

PHPBB3-11305
[ticket/11305] Use phpbb_create_default_container.

PHPBB3-11305
[ticket/11305] Adjust comment.

PHPBB3-11305
[ticket/11305] Define hook finder as a service on the container.

PHPBB3-11305
[ticket/11305] Check for $cache being null before using it in db drivers.

There is no reason why db drivers must have a cache to work.
They query the database, that part works without caches.

PHPBB3-11305
[ticket/11305] Mock container for cache driver in functional create_user()

create_user has calls to fetch the cache driver from the container. This
PR mocks the container and returns a null cache driver in that case.

PHPBB3-11305
Merge remote-tracking branch 'p/ticket/11305' into develop

* p/ticket/11305:
  [ticket/11305] Mock container for cache driver in functional create_user()
  [ticket/11305] Check for $cache being null before using it in db drivers.
  [ticket/11305] Define hook finder as a service on the container.
  [ticket/11305] Adjust comment.
  [ticket/11305] Use phpbb_create_default_container.
  [ticket/11305] Create a normal container during final installation step.
  [ticket/11305] Retrieve cache driver from container rather than cache service.
  [ticket/11305] Extract hook finder from cache service.