Extension matcher documentation doesn't generate a link to the xds Matcher type

*Title*: Extension matcher documentation doesn't generate a link to the xds Matcher type

*Description*:

In the [extension matcher docs](https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/common/matching/v3/extension_matcher.proto.html), the documentation generator doesn't generate a reference link for the `xds.type.matcher.v3.Matcher`.

The actual sphinx doc looks like this. Note How there is no `:ref:` generated for the `xds.type.matcher.v3.Matcher` type:
```rst
.. code-block:: json

{
"matcher": "{...}",
"xds_matcher": "{...}",
"extension_config": "{...}"
}

.. _envoy_v3_api_field_extensions.common.matching.v3.ExtensionWithMatcher.matcher:

matcher
(:ref:`config.common.matcher.v3.Matcher `) The associated matcher. This is deprecated in favor of xds_matcher.


.. _envoy_v3_api_field_extensions.common.matching.v3.ExtensionWithMatcher.xds_matcher:

xds_matcher
(.xds.type.matcher.v3.Matcher) The associated matcher.


.. _envoy_v3_api_field_extensions.common.matching.v3.ExtensionWithMatcher.extension_config:

extension_config
(:ref:`config.core.v3.TypedExtensionConfig `, *REQUIRED*) The underlying extension config.


```