Change flags for managing controllers from a custom
enabled/auto/disabled type to booleans. By default, all controllers are
enabled. If a controller's disable flag is set, it is disabled. Enabled
controllers that have an auto loader are loaded if they are enabled and
their auto loader indicates they should load.

Remove the KongStateEnabled flag. This was a leftover from an earlier
design where the controller managed Kong state information via a special
Secret. It had no remaining associated code and was only present in
configuration.

Rename controller flags to reflect that they disable controllers when
set.

Remove enablement status type, associated utility functions, and custom
flag handler.

Move deferred body close checks after the error checkers. If an error is
present, no body exists, and the deferred attempt to close it segfaults.

Change the controller flags from disablers to enablers and flip the
logic that handles them.

Remove unnecessary pointer usage.

Co-authored-by: Michał Flendrich <[email protected]>