Fix pointers and C-like layout in varying parameters (#8425)

Closes #8409, but ended up being more about fixing another bug. While
the issue itself seems to only be a simple typo fix (see second commit
in this PR), I found out during writing a test that pointers never got
correct locations regardless of layout. Their locations were always
assigned to zero due to lacking a resource usage entry in `TypeLayout`.
They were also missing the `Flat` decoration, so I went ahead and added
that too.

I can split this up into two separate PRs if that's preferred; both
aspects just share a test right now and fix a similar-looking issue in
the resulting SPIR-V.

0 files changed, 0 insertions, 0 deletions