AstGen: emit debug stmt for try

This improves the following test case:

```zig
pub fn main() !void {
    try foo();
}

fn foo() !void {
    return error.Bad;
}
```

The error return trace now points to the `try` token instead of pointing
to the foo() function call, matching stage1.

Closes #12308.
feb90f6ed4Andrew Kelley committed on 8/9/2022, 4:12:04 AMparent0648177
2 files changedLine totals unavailable