(PTFE-2499) Add variable to deploy service systemd (#702)

Since 18/06/2025 ubuntu runner on Jammy can't launch there systemd
service because de base64 $JIT_CONFIG is to large for systemd.

Here we push the base64 in an env var which will be use by the command
line.

This type of systemd service has been test both on ubuntu22.04 and
ubuntu24

Author: matthiasL-scality

runner_manager/bin/startup.sh

@@ -90,7 +90,8 @@ Description=GitHub Actions Runner
 After=network.target
 
 [Service]
-ExecStart=/bin/bash /home/actions/actions-runner/run.sh --jitconfig \"${JIT_CONFIG}\"
+Environment=\"JIT_BASE64=${JIT_CONFIG}\"
+ExecStart=/bin/bash /home/actions/actions-runner/run.sh --jitconfig \"${JIT_BASE64}\"
 User=actions
 WorkingDirectory=/home/actions/actions-runner
 KillMode=process