[clang] add APValue type check in `TryPrintAsStringLiteral`

Fixes https://github.com/llvm/llvm-project/issues/57013

https://reviews.llvm.org/D115031 improved printing of non-type template
parameter args. But checking if the end of Inits is 0 without checking
if APValue is an integer, causes clang to segfault. This patch adds
the code to check the type. (May not be a proper bugfix.)

Reviewed By: aaron.ballman, lichray

Differential Revision: https://reviews.llvm.org/D131466