[Native] Remove CMake installation logic from native/cpp

Summary:
Not strictly needed since we don't install the
native cpp modules separately.

add_subdirectory was added to android/app/CMakeLists.txt
to ensure that the CMake logic is compatible.

Depends on D6484

Test Plan: Android gate passes

Reviewers: max, ashoat, varun, atul

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D6498