Cylc/Cylc: Cylc-7.5.0

Many changes and fixes including: arbitrary suite and task metadata items that can be passed to event handlers; new shell function to abort a job with a custom message that can be passed to task failed event handlers; removed auto-fallback to HTTP communications; many validation and runtime efficiency improvements; new task runtime reporting tool; fix cylc cat-log "open in editor" for remote jobs; ensure that task parameter values are exported, in task job scripts, before the user environment section; and more - please see CHANGES.md for details.