Move creation of deapexer modules to separate mutator

Previously, deapexer modules were created by the LoadHook which meant
that the deapexer module could not use any information derived from the
dependencies of the prebuilt_apex/apex_set modules. This change moves
the creation into a separate mutator that runs after
ComponentDepsMutator and before DepsMutator. That means that a follow
up change can use information from dependencies added by the former
mutator in order to create the deapexer module and the deapexer module
can itself add dependencies onto other modules.

This change also dedups the logic to determine whether a deapexer
module is needed by pushing it down into the createDeapexerModule
method which was renamed to createDeapexerModuleIfNeeded to reflect its
conditional nature.

Bug: 187266082
Test: m nothing
      m SOONG_CONFIG_art_module_source_build=false nothing
Change-Id: I65316473ff1e4b2827ff48ab5a870a8ce5c0475a