CLD-7841 Optimize E2E testing costs (#27883)

* Utilize free runners for E2E tests, report back to PR on run completion
* Increase test stability on smaller instances
* Merge worker reports
* merge start+prepare steps
* upgrade keycloak
* increase test timeouts
* Add video recording to report artifacts

Co-authored-by: Saturnino Abril <5334504+saturninoabril@users.noreply.github.com>

---------

Co-authored-by: Saturnino Abril <5334504+saturninoabril@users.noreply.github.com>

server/build/docker/keycloak/kc-healthcheck.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -eu -o pipefail
+
+/opt/keycloak/bin/kcadm.sh config credentials -x --server http://localhost:8080 --realm master --user "$KEYCLOAK_ADMIN" --password "$KEYCLOAK_ADMIN_PASSWORD"
+/opt/keycloak/bin/kcadm.sh get realms/mattermost >/dev/null