test: fix ups for various deprecated fields (#8068)

Takeaways: we've lost the ability to do empty regex (which was covered in router tests and is proto constraint validated on the new safe regex) as well as negative lookahead (also covered in tests) along with a host of other things conveniently documented as not supported here: https://github.com/google/re2/wiki/Syntax

Otherwise split up a bunch of tests, duplicated and tagged a bunch of tests, and cleaning up after we finally can remove deprecated fields again will be an order of magnitude easier.

Also fixing a dup relnote from #8014

Risk Level: n/a (test only)
Testing: yes. yes there is.
Docs Changes: no
Release Notes: no

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

docs/root/intro/version_history.rst

@@ -29,7 +29,6 @@ Version history
 * http: added the ability to reject HTTP/1.1 requests with invalid HTTP header values, using the runtime feature `envoy.reloadable_features.strict_header_validation`.
 * http: changed Envoy to forward existing x-forwarded-proto from upstream trusted proxies. Guarded by `envoy.reloadable_features.trusted_forwarded_proto` which defaults true.
 * http: added the ability to configure the behavior of the server response header, via the :ref:`server_header_transformation<envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.server_header_transformation>` field.
-* http: changed Envoy to forward existing x-forwarded-proto from downstream trusted proxies. Guarded by `envoy.reloadable_features.trusted_forwarded_proto` which defaults true.
 * http: added the ability to :ref:`merge adjacent slashes<envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.merge_slashes>` in the path.
 * listeners: added :ref:`continue_on_listener_filters_timeout <envoy_api_field_Listener.continue_on_listener_filters_timeout>` to configure whether a listener will still create a connection when listener filters time out.
 * listeners: added :ref:`HTTP inspector listener filter <config_listener_filters_http_inspector>`.