This commit removes a distinction in how dependency objects are checked for
cycles in the resulting graph depending on whether they are part of the
initially loaded configuration during process startup or as part of a runtime
update.
The DependencyCycleChecker helper class is extended with a mechanism that
allows additional dependencies to be considered during the cycle search. This
allows using it to check for cycles before actually registering the
dependencies with the checkables.
The aforementioned case-distinction for initial/runtime-update config is
removed by making use of the newly added BeforeOnAllConfigLoaded signal to
perform the cycle check at once for each batch of dependencies inside
ConfigItem::CommitNewItems() for both cases now. During the initial config
loading, there can be multiple batches of dependencies as objects from apply
rules are created separately, so parts of the dependency graph might be visited
multiple times now, however that is limited to a minimum as only parts of the
graph that are reachable from the newly added dependencies are searched.