Add basic concept of module and module registry + dependency graph

Modules have protected lifecycle functions.
Modules are identified by a factory object that knows how to construct them.
Modules can indicate which dependencies they have.

Dependencies are started before their dependent modules.
Don't support incremental module stop for the moment - it's all or nothing.

Test: atest --host bluetooth_test_gd:ModuleTest
Change-Id: I026b9e893501506a6cea8387941b3a9424a9bec9