Add MB configs and mixins for chromium.lkgr bots.
Add MB configs and mixins for chromium.lkgr bots.

This adds a bunch of sanitizer-specific configs for the chromium.lkgr
bots, which mostly upload builds for fuzz testing.

R=brettw@chromium.org, aneeshm@chromium.org
BUG=481692

Review URL: https://codereview.chromium.org/1872213002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#388084}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk