libbinder : Adding new type TransportFd

Adding a new struct TransportFd which will contain unique_fd and
polling state of file descriptor. This will be useful in detecting
if all the descriptors are being polled. unique_fd and borrowed_fd
are replaced in these changes.

Test: m
Test: m libbinder binderRpcTest && atest binderRpcTest
Test: trusty/vendor/google/aosp/scripts/build.py  --test
      "boot-test:com.android.trusty.binder.test" qemu-generic-arm64-test-debug
Bug: 218518615
Change-Id: Id108806b98184582e5d93186b3b1884017c441ea