Motivation:
Current implementation of UniqueFd can be used in a different ways,
making analytical tracking of FD lifecycle much harder than it may be.
Keep this part clean is very important, since any wrong code may open
a hard-to-detect runtime bugs and fd leaks, which may accidentally slip
into the production.
Implementation:
1. Combine UniqueFd anf OutputFd into single class.
2. Reduce the API to be minimal and sufficient.
3. Document the API and use cases.
4. Move to utils/UniqueFd.h.
5. dup(fd) was replaced with fcntl(fd, F_DUPFD_CLOEXEC)) to
address clang-tidy findings. Find more information at [1]
[1]: https://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-dup.html
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
