Revert "Allow dependencies from platform variants to APEX modules."

Revert submission 1658000

Reason for revert: Breaks full-eng build: b/184239856
Reverted Changes:
I4f8ead785:Avoid internal APEX stubs for libsigchain and clea...
I68affdf69:Allow dependencies from platform variants to APEX ...
I54b33784e:Rename libdexfile_external_static to libdexfile_st...
Id68ae9438:libdexfile_external is being replaced by libdexfil...
I12ac84eb4:libdexfile_external is replaced by libdexfile.
If05dbffc8:Rename libdexfile_external_static to libdexfile_st...
Ia011fa3a8:Merge libdexfile_external into libdexfile.

Change-Id: If494dc5385042a4620a76a9eadc1613ae0eb1655