feat: Add --no-rebot option and #SLEEP keyword, fix caching bug

[joonaskuisma]

• Added a new --no-rebot option that prevents result merging, allowing users to handle it manually later. This was requested in issue Allow the pabot results to be left without aggregating them. #571 to ensure resource availability.
• Added a #SLEEP keyword, which can be used in the --ordering file to introduce delays between subprocess startups. This was requested in issues pabot first tests batch delay start #500 and required a support adding new flag which will wait before trigger next suite #592.
• Fixed a caching mechanism bug related to .pabotsuitenames (Issue with the .pabotsuitenames caching mechanism. #619).

Closes #571, #500, #592, #619. 🚀