Rebrand various CI scripts and modules

This replaces Riot with Element in various CI scripts, modules, parameters, etc.
This _should_ be the last major rebranding pass (hopefully).

Fixes https://github.com/vector-im/element-web/issues/14894

test/end-to-end-tests/riot/install-webserver.sh

@@ -1,21 +0,0 @@
-#!/bin/bash
-set -e
-
-BASE_DIR=$(cd $(dirname $0) && pwd)
-cd $BASE_DIR
-# Install ComplexHttpServer (a drop in replacement for Python's SimpleHttpServer
-# but with support for multiple threads) into a virtualenv.
-(
-    virtualenv -p python3 env
-    source env/bin/activate
-
-    # Having been bitten by pip SSL fail too many times, I don't trust the existing pip
-    # to be able to --upgrade itself, so grab a new one fresh from source.
-    curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
-    python get-pip.py
-    rm get-pip.py
-
-    pip install ComplexHttpServer
-
-    deactivate
-)