libdmabufinfo: Make public ReadDmaBufMapRefs() and ReadDmaBufFdRefs()

Remove AppendDmaBufInfo() which fails if either reading dmabuf FDs
or maps fails.

Allow clients to decide how to handle each of these fail cases by
exposing ReadDmaBufMapRefs() and ReadDmaBufFdRefs()

Bug: 181976677
Test: dmabufinfo_test
Change-Id: I6d6c3aa25dc73c7b18c1e65ab09a985e89990648
4 files changed