Add lxml wheel for Windows DebugVisualizer presubmit support

The lxml package lets us validate .natvis files against the schema.

See: crrev.com/c/6533151

It is already available on CIPD and is being used by chromium infra:
- https://chrome-infra-packages.appspot.com/p/infra/python/wheels/lxml
- https://source.chromium.org/chromium/infra/infra_superproject/+/main:infra/go/src/go.chromium.org/chromiumos/config/.vpython3;l=163-166;drc=faae440af665c1ee2b26b3e25d52bad6a5d144ae

Change-Id: Ic19ae47268612230cf9db94c37792c989964e58f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6593971
Commit-Queue: Michael Tang <tangm@microsoft.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Brian Ryner <bryner@google.com>

.vpython3

@@ -87,4 +87,11 @@ wheel: <
 wheel: <
   name: "infra/python/wheels/hjson-py2_py3"
   version: "version:3.1.0"
+>
+
+# Used by:
+#   tools/win/DebugVisualizers/PRESUBMIT.py
+wheel: <
+  name: "infra/python/wheels/lxml/${vpython_platform}"
+  version: "version:4.9.3"
 >