ANDROID: GKI: Protect exports of protected GKI modules

Implement support for protecting the exported symbols of
protected GKI modules.

Only signed GKI modules are permitted to export symbols
listed in the android/abi_gki_protected_exports file.
Attempting to export these symbols from an unsigned module
will result in the module failing to load, with a
'Permission denied' error message.

Bug: 232430739
Test: TH
Change-Id: I3e8b330938e116bb2e022d356ac0d55108a84a01
Signed-off-by: Ramji Jiyani <ramjiyani@google.com>