Fix _RunRustFmt command line length issues and Windows compatibility

* Split file paths into batches using _SplitArgsByCmdLineLimit to avoid
  command line length limits.
* Add shell=False to subprocess call, because depot_tools-bundled
  subprocess2 wrapper sets it to True on Windows which prevents the use
  of full 32k command line limit.

Change-Id: Ifdd470087e34b1d9de54309c7915691e3e624f0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/7062914
Reviewed-by: Scott Lee <ddoman@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Aleksei Khoroshilov <akhoroshilov@brave.com>

git_cl.py

@@ -6922,11 +6922,11 @@ def _RunRustFmt(opts, paths, top_dir, diffs):
     cmd = [rustfmt_tool, f'--config-path={rustfmt_toml_path}']
     if opts.dry_run:
         cmd.append('--check')
-    cmd += paths
-    rustfmt_exitcode = subprocess2.call(cmd)
 
-    if opts.dry_run and rustfmt_exitcode != 0:
-        return 2
+    for paths_batch in _SplitArgsByCmdLineLimit(paths):
+        rustfmt_exitcode = subprocess2.call(cmd + paths_batch, shell=False)
+        if opts.dry_run and rustfmt_exitcode != 0:
+            return 2
 
     return 0