ART: Factor out IMT from ArtMethod

Move IMT Conflict Table to its own file. Move IMT index computation to
ImTable.

In preparation for code using this independent of specific ArtMethods.

Bug: 31594153
Test: m test-art-host
Change-Id: Ifd6e304bb86724c5284984c4655c43d3af357f84
diff --git a/runtime/arch/stub_test.cc b/runtime/arch/stub_test.cc
index 507dbf0..3424e3c 100644
--- a/runtime/arch/stub_test.cc
+++ b/runtime/arch/stub_test.cc
@@ -22,6 +22,7 @@
 #include "class_linker-inl.h"
 #include "common_runtime_test.h"
 #include "entrypoints/quick/quick_entrypoints_enum.h"
+#include "imt_conflict_table.h"
 #include "linear_alloc.h"
 #include "mirror/class-inl.h"
 #include "mirror/string-inl.h"