Similar to msan.h, asan should get its own header file such that the
functionality can be reused.

R=ahaas@chromium.org

Bug: v8:7570
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: Ib81e4ff4b1d08158df7730c32345d4facf9453b0
Reviewed-on: https://chromium-review.googlesource.com/1046656Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53073}