This is a major breaking change that will affect all users of
reconciler-runtime. There does not appear to be a way to transparently
apply generics to an existing API that allows users to opt-in over time.

User defined functions are now compile-time type checked, and IDEs will
be able to offer completion for method signatures. At runtime these
functions are directly invoked and are no longer called by reflection.
Runtime type checking has been removed.

Changes:

- All existing deprecations are removed
- All Reconcilers and SubReconcilers now operate on generic types of
  client.Object.
- All reconciler Type/ChildType/ChildListType fields are now optional.
  They are only required if the generic type is an interface, or to
  define the apiVersion/kind for an Unstructured type.
- SyncReconciler#Sync and #Finalize methods are split into two fields,
  one that is _WithResult and the default method which only returns an
  error.

Signed-off-by: Scott Andrews <andrewssc@vmware.com>

The Type field for CastResource is completely redundant with the generic
types. We can also go a step further and avoid converting the resource
when the CastType is an interface, because we know all concrete types
are already compatible and only need to be cast, saving a lot of
overhead.

Signed-off-by: Scott Andrews <andrewssc@vmware.com>

Signed-off-by: Scott Andrews <andrewssc@vmware.com>

This means that the value of Resource and ExpectedResource must be the
same type as the reconciler handles.

No longer can a die be passed directly and unwrapped inside the test.
While this behavior was extremely convenient, it created expectations
that may not be true in other cases and depends on DeepCopyObject on the
die returning a different type than the method was called on.

Signed-off-by: Scott Andrews <andrewssc@vmware.com>