Rephrase *cycle time* to *cycle point*

Fix tests for cylc 6.
When checking whether a suite is running or not, allow reasons to
contain all lines of the `pgrep` command.
Fix `date_format` in `rose.date`.

Simply return `TimePoint` object if format string is `None`.
Fix `rose_prune` test
Improve stability of tests
Rose Bush templates: Z syntax no longer required

We can now assume that cylc stores date time correctly.
rose date: fix unnecessary `if`
Merge pull request #1323 from matthewrmshin/fix-t-for-cylc-6

Rephrase cycle time to cycle point