Feature/improved timer events

[essweine]

1. Switch timer definition formats to ISO 8601
2. Correct behavior of cycle timers

[danfunk]

Very thorough. Will need to test against CR-Connect to see how it holds up to those files. I do wonder if an existing library could not parse these values and would have examined more case.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
6 Code Smells

93.2% Coverage
0.0% Duplication

[essweine]

I looked at several ISO 8601 parsing libraries, but they were generally missing support for something I needed (recurring intervals most commonly) and they didn't necessarily actually handle time deltas -- you might get something like my parsed_duration, but not an actual timedelta which must be based on an actual time; that was the hard part (the string parsing is not complicated). I found one that had support for recurrences, but it was via a generator (which is a very sensible solution, I'm basically doing the same thing) but if used it, I'd have to serialize it, so that was a hard pass.