This migrates test configs for all remaining trybots.

All migrated builders are not on CQ, hence, they don't run regularly.
Therefore, some shard configs are too low by now and are also upgraded
in this CL to match their CI counterparts.

This also sets the --gc-stress flag for all tests on gc stress builders
explicitly, since the infra-side configuration (which sets it per
builder) will be deleted soon.

NOTRY=true

Bug: chromium:830557
Change-Id: Id8a9505fcd2c848ec659c7401cbbe9224feaf5d2
Reviewed-on: https://chromium-review.googlesource.com/1065674Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53275}