[clang] [clang-tools-extra] [lldb] [clang] Reland: fix getTemplateInstantiationArgs (PR #208285)

[Nathan Corbyn via cfe-commits]

cofibrant wrote:

What I mean is, it would be worth completing a successful stage 2 locally at desk before attempting to reland again. 

https://github.com/llvm/llvm-project/pull/208285