Move RootCanal to tools/ folder

The new directory is added as a new visibility rules
instead of replacing the old one to avoid an automerger
conflict. The old path will be removed in a following CL.

Test: m root-canal
Change-Id: Ic6489b57d0b03cf6f0c7cd400b578394cdea300d
diff --git a/libbacktrace/Android.bp b/libbacktrace/Android.bp
index dded0ae..e30ef5e 100644
--- a/libbacktrace/Android.bp
+++ b/libbacktrace/Android.bp
@@ -131,6 +131,7 @@
         "//packages/modules/Bluetooth/system/vendor_libs/test_vendor_lib",
         "//system/core/init",
         "//system/core/libutils",
+        "//packages/modules/Bluetooth/tools/rootcanal",
     ],
     min_sdk_version: "apex_inherit",
     vndk: {