Fix various missing includes in perfetto

Several files in perfetto refer to C++ standard library symbols defined
in headers that are not explicitly included. Right now, perfetto
compiles without errors because these includes are provided via
transitive includes in other libc++ headers. However, these transitive
includes are not guaranteed to exist according to the C++ standard, and
will *not* exist in certain contexts (e.g. building against libc++ using
-fmodules).

Bug: chromium:543704
Change-Id: I7ea562601b5d02fef614201afbe0286b30af76ab