Switch libbacktrace new unwinder.

Update the backtrace leak tests to share a map since this is the most
common way it will be used, and it runs much faster.

Remove the CreateNew functions, and references to them.

Remove benchmarks of CreateNew functions.

Test: Builds, ran new unit tests, ran art tests.

Change-Id: I4a25a412f1a74c6d43aebbebbf32ead20ead8f94
diff --git a/libbacktrace/UnwindStackMap.cpp b/libbacktrace/UnwindStackMap.cpp
index e7e5e4c..25e5002 100644
--- a/libbacktrace/UnwindStackMap.cpp
+++ b/libbacktrace/UnwindStackMap.cpp
@@ -103,7 +103,7 @@
 //-------------------------------------------------------------------------
 // BacktraceMap create function.
 //-------------------------------------------------------------------------
-BacktraceMap* BacktraceMap::CreateNew(pid_t pid, bool uncached) {
+BacktraceMap* BacktraceMap::Create(pid_t pid, bool uncached) {
   BacktraceMap* map;
 
   if (uncached) {