ART: Introduce thread-current-inl.h

Factor out Thread::Current() code into its own -inl file to remove
transitive includes.

This requires at the same time correcting mutex.h, i.e., moving
some functions into mutex-inl.h.

Test: m test-art-host
Change-Id: I88f888b604e0897368d9b483edce6ce4332dd9c9
diff --git a/compiler/optimizing/intrinsics_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index b511c5a..c4d7cc8 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -28,7 +28,7 @@
 #include "mirror/reference.h"
 #include "mirror/string-inl.h"
 #include "scoped_thread_state_change-inl.h"
-#include "thread-inl.h"
+#include "thread-current-inl.h"
 #include "utils/arm64/assembler_arm64.h"
 
 using namespace vixl::aarch64;  // NOLINT(build/namespaces)