CRASH: `Fatal error: failed to create trace file ` ... `window.0000` ...., with `window.0001` directory

**Describe the bug**
From time to time I have a DynamoRIO crash with an error message along the lines of

````
Fatal error: failed to create trace file /root/palmerdabbelt/runs/django-mini-drmemtrace_interval-1.OflDffjb/drmemtrace.uwsgi.1937455.5528.dir/raw/window.0000/drmemtrace.uwsgi.1937455.0618.raw.lz4
````

The resulting trace directory has a `window.0001` file instead, so that error message itself seems somewhat sane. I think it's a race -- `init_offline_dir()` has an unprotected load of the trace window ID:

````
if (has_tracing_windows())
open_new_window_dir(tracing_window.load(std::memory_order_acquire));
````

and if the trace window has moved

The issue goes away if I just stick a second `mkdir` in there

````
diff --git a/clients/drcachesim/tracer/output.cpp b/clients/drcachesim/tracer/output.cpp
index 63a8b9353..c4e40ff00 100644
--- a/clients/drcachesim/tracer/output.cpp
+++ b/clients/drcachesim/tracer/output.cpp
@@ -398,6 +398,11 @@ open_new_thread_file(void *drcontext, ptr_int_t window_num)
dr_snprintf(windir, BUFFER_SIZE_ELEMENTS(windir), "%s%s" WINDOW_SUBDIR_FORMAT,
logsubdir, DIRSEP, window_num);
NULL_TERMINATE_BUFFER(windir);
+
+ if (!file_ops_func.create_dir(windir))
+ FATAL("Fiailed to create window subdir %s\n", windir);
+ NOTIFY(2, "Created new window dir %s\n", windir);
+
dir = windir;
} else if (data->file != INVALID_FILE)
return false;
````

but I think that warrants a little refactoring to remove the duplicate calls (and code from `open_new_window_dir()`). I'll post a patch, unless someone has a better idea of what's going on.

**To Reproduce**
(Happy to write more, but I think I'm going to fix it myself.)

1. I'm using DCPerf's Django-mini workload.
2. Running with `-trace_for_insns 1000` makes this happen almost always.

It's fine without any client, and I haven't tried a debug build.

**Expected behavior**
I get traces ;)

**Screenshots or Pasted Text**
````
Fatal error: failed to create trace file /root/palmerdabbelt/runs/django-mini-drmemtrace_interval-1.OflDffjb/drmemtrace.uwsgi.1937455.5528.dir/raw/window.0000/drmemtrace.uwsgi.1937455.0618.raw.lz4
````

**Versions**
I'm running github's main branch from this morning, on an aarch64 machine (CentOS Stream 9-ish).