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

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

I would highlight the only actionable item I have right now is that crash reproducer from the stage2 failure.

(besides the couple of crashes-on-invalid generated by fuzzer I missed from the last Reland)

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