Move tombstone_proto_to_text out of libdebuggerd.

This is done so that we could depend on it elsewhere without needing all the unrelated methods.
Needed for ag/24553347

Bug: 296207744
Test: refactoring build
Change-Id: I7c6733208f3ae63ba9559753a24cffcb8e1b9d1e
8 files changed