Remove mirror:: and ArtMethod deps in utils.{h,cc}

The latest chapter in the ongoing saga of attempting to dump a DEX
file without having to start a whole runtime instance.  This episode
finds us removing references to ArtMethod/ArtField/mirror.

One aspect of this change that I would like to call out specfically
is that the utils versions of the "Pretty*" functions all were written
to accept nullptr as an argument.  I have split these functions up as
follows:
1) an instance method, such as PrettyClass that obviously requires
this != nullptr.
2) a static method, that behaves the same way as the util method, but
calls the instance method if p != nullptr.
This requires using a full class qualifier for the static methods,
which isn't exactly beautiful.  I have tried to remove as many cases
as possible where it was clear p != nullptr.

Bug: 22322814
Test: test-art-host
Change-Id: I21adee3614aa697aa580cd1b86b72d9206e1cb24
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 1e69966..59cc009 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -2295,7 +2295,7 @@
   ScopedObjectAccess soa(Thread::Current());
   os << "["
      << " is_valid=" << rhs.IsValid()
-     << " type=" << (!rhs.IsValid() ? "?" : PrettyClass(rhs.GetTypeHandle().Get()))
+     << " type=" << (!rhs.IsValid() ? "?" : mirror::Class::PrettyClass(rhs.GetTypeHandle().Get()))
      << " is_exact=" << rhs.IsExact()
      << " ]";
   return os;