[gn] Add required sanitizer blacklist files.

Splitt of CL:
https://codereview.chromium.org/2188693002/#ps100001

Switching to GN is blocked on test errors. These files are
required for compilation and allow looking into the test
errors locally.

BUG=chromium:474921
NOTRY=true

Review-Url: https://codereview.chromium.org/2190863003
Cr-Commit-Position: refs/heads/master@{#38130}

tools/memory/asan/blacklist.txt

+# The rules in this file are only applied at compile time. If you can modify the
+# source in question, consider function attributes to disable instrumentation.
+#
+# Please think twice before you add or remove these rules.
\ No newline at end of file

tools/memory/tsan_v2/ignores.txt

+# The rules in this file are only applied at compile time. If you can modify the
+# source in question, consider function attributes to disable instrumentation.
+#
+# Please think twice before you add or remove these rules.
+# Data races should typically go to suppressions.txt.
\ No newline at end of file