[Core] Generalize ValueObject::IsRuntimeSupportValue

Summary:
Instead of falling back to ObjCLanguageRuntime, we should be falling
back to every loaded language runtime. This makes ValueObject more
language agnostic.

Reviewers: labath, compnerd, JDevlieghere, davide

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D63240

llvm-svn: 364845