This patch handles default integral non-type template parameters.
After this patch the clang TypePrinter will omit default integral
template arguments when the `PrintingPolicy::SuppressDefaultTemplateArgs`
option is specified and sets us up to be able to re-use
`clang::isSubstitutedDefaultArgument` from the DWARF CodeGen
component.
Differential Revision: https://reviews.llvm.org/D139986