upload_symbols: rewrite in python

We want to do more stuff with upload_symbols.  The current bash code is
limiting us though.  Rewrite it in python and use chromite libraries.

BUG=chromium:209442
BUG=chromium:213204
TEST=`./buildbot/run_tests` passes
CQ-DEPEND=CL:57182

Change-Id: Ib10cb9c48bf2bf6f06a7b0400af4b1fe54ede856
Reviewed-on: https://gerrit.chromium.org/gerrit/58625
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
4 files changed