Bugzilla

As a part of Bug 1772213, we discovered we needed a server for testing with the following behaviour: Http2 Server without h2 websocket support, but has h1.1 websocket support. So when we try to connect to it it is capable of falling back to h1.1 for the websocket connection.

We briefly considered creating a new server similar to the existing [NodeWebSocketHttpServer](https://searchfox.org/mozilla-central/source/netwerk/test/unit/head_servers.js#676) and while the solution for our purposes will likely be similar it was considered out of scope of 1772213.

In summary the essence of this task are:
1. Build the server capable of doing this.
2. Add a test to our websocket xpcshell-test suite that exercises the desired behavior.

As a part of Bug 1772213, we discovered we needed a server for testing with the following behaviour: Http2 Server without h2 websocket support, but has h1.1 websocket support. So when we try to connect to it it is capable of falling back to h1.1 for the websocket connection.

We briefly considered creating a new server similar to the existing [NodeWebSocketHttpServer](https://searchfox.org/mozilla-central/source/netwerk/test/unit/head_servers.js#676) and while the solution for our purposes will likely be similar it was considered out of scope of Bug 1772213.

In summary the essence of this task are:
1. Build the server capable of doing this.
2. Add a test to our websocket xpcshell-test suite that exercises the desired behavior.