Split APEX ABI dumps from implementation ABI dumps

This commit adds a rule that builds APEX ABI dumps separately from the
implementation libraries' ABI dumps. The rule takes the
export_include_dirs and the symbol_file of the stubs as parameters.
The dump paths are tagged with "APEX" in lsdump_paths.txt. The script
updating the prebuilt reference dumps can differentiate the APEX dumps
from the opt-in dumps tagged with "PLATFORM".

This commit also adds an ABI diff rule. Soong compares the APEX ABI
dumps with the reference dumps in version 35. It compares the
implementation dumps with the reference dumps in old versions.

Bug: 333532038
Test: make
Change-Id: I76902a8e3b7d0e96a5ad756f493924371cd7ad3c