user_activity: Created utility module for grouping parsing functions.

The modules contains the functions that do the parsing for the pprof top
and tree, CWP data and Chrome OS groups files.

BUG=None
TEST=utils_unittest passes

Change-Id: Ida94a2d456250afe4630a146349937eb0bab0767
Reviewed-on: https://chrome-internal-review.googlesource.com/291201


Reviewed-by: Luis Lozano <llozano@chromium.org>
Reviewed-by: Evelina Dumitrescu <evelinad@google.com>
Tested-by: Evelina Dumitrescu <evelinad@google.com>
Reviewed-on: https://chromium-review.googlesource.com/435915


Commit-Ready: Luis Lozano <llozano@chromium.org>
Tested-by: Luis Lozano <llozano@chromium.org>