[clang] [Clang] Consider default template arguments when synthesizing CTAD guides (PR #147675)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

This seems reasonable/right to me, but please give @mizvekov a chance to double-check, he's more familiar with deduction than I am.

https://github.com/llvm/llvm-project/pull/147675