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.

test/stack_traces.zig

@@ -22,6 +22,7 @@ pub fn addCases(cases: *tests.StackTracesContext) void {
         .ReleaseSafe = .{
             .exclude_os = .{
                 .windows, // segfault
+                .linux, // defeated by aggressive inlining
             },
             .expect = 
             \\error: TheSkyIsFalling