tombstoned: change path for traces from "anr_" to "trace_"

The only case where tombstoned creates files for java traces is
when the process is signalled "by hand" using "shell kill -3", or
by the program itself. Such traces do not correspond to an ANR, so
name those files "trace_XX".

When dumpstate / system_server want to dump java traces, they set up
a tombstoned intercept and manage the lifetime of any associated file
that themselves.

Bug: 32064548
Test: manual, debuggerd_test
Change-Id: I97006ec7c0cd35de4b9564f535e77af846cc3891
diff --git a/debuggerd/tombstoned/tombstoned.cpp b/debuggerd/tombstoned/tombstoned.cpp
index b920ebc..4249e13 100644
--- a/debuggerd/tombstoned/tombstoned.cpp
+++ b/debuggerd/tombstoned/tombstoned.cpp
@@ -172,7 +172,7 @@
                    1 /* max_concurrent_dumps */);
 
 /* static */ CrashQueue* const CrashQueue::java_trace =
-    (kJavaTraceDumpsEnabled ? new CrashQueue("/data/anr", "anr_" /* file_name_prefix */,
+    (kJavaTraceDumpsEnabled ? new CrashQueue("/data/anr", "trace_" /* file_name_prefix */,
                                              64 /* max_artifacts */, 4 /* max_concurrent_dumps */)
                             : nullptr);