Inside a nosuspend block, emit function calls as nosuspend calls.
Also inside a comptime block, emit function calls as comptime calls.
Also emit `async foo()` calls as async calls.

Remove compile error for `nosuspend` block inside `suspend` block.
Instead of implicitly treating every `suspend` block also as a
`nosuspend` block (which would make sense), we leave suspension points
as compile errors, to hint to the programmer about accidents. Of course
they may then assert `nosuspend` by introducing a block within their
suspend block.

To make room in `Zir.Inst.Tag` I moved `typeof_peer` and `compile_log`
to `Extended`.