shell: Make LISA_CONF and LISA_RESULT_ROOT modifiable
Allow modifying them before source init_env like other variables, so it's easy to pre-configure an environment.
GitLab Maintenance scheduled for Thursday, 18th December 2025, from 7:00 AM to 10:00 AM BST. GitLab will be in read-only mode and experience short periods of complete downtime (up to 20 minutes) during this window.
Allow modifying them before source init_env like other variables, so it's easy to pre-configure an environment.