Infrastructure for obsolete methods

This adds some of the structures and functions needed to eventually
support obsolete methods. Specifically this adds the code to create
and iterate through the obsolete dex-cache maps of classes and
re-organizes the redefinition code to be more sensible and extensible.

Bug: 32369913
Test: ./test/run-test --host 902
Test: mma -j40 test-art-host

Change-Id: I93d60fa66e7512e8b059cdf42af8a56e93ef4bd7
diff --git a/runtime/modifiers.h b/runtime/modifiers.h
index dd32df6..a1110d9 100644
--- a/runtime/modifiers.h
+++ b/runtime/modifiers.h
@@ -67,6 +67,10 @@
 
 // Set by the verifier for a method that could not be verified to follow structured locking.
 static constexpr uint32_t kAccMustCountLocks =        0x02000000;  // method (runtime)
+// Set to indicate that the ArtMethod is obsolete and has a different DexCache from it's declaring
+// class.
+// TODO Might want to re-arrange some of these so that we can have obsolete + intrinsic methods.
+static constexpr uint32_t kAccObsoleteMethod =        0x04000000;  // method (runtime)
 static constexpr uint32_t kAccIntrinsic  =            0x80000000;  // method (runtime)
 
 // Special runtime-only flags.