Add start and end datetime to schedules

[grahamia]

Is your feature request related to a problem? Please describe.
To save on cost and the inconvenience of having to arrange deployments etc at the right time (to start and end a training schedule) it would be nice to be able to specify the start and end time for a schedule to run.

Describe the solution you'd like
In the runconfiguration resource as part of the schedule trigger you should be able to optionally also set a start and end date, therefore also transferred into the runschedule resource the same information. Given this would need a new version of the resources as string will need to a struct containing the crontab and optional start and end datetimes.

These should be optional and if not given then as it is now, the schedule starts on deployment and doesn't end until removed.

Additional context
Add any other context or screenshots about the feature request here.

Vertex AI provider accepts start and end datetime as parameters to its createSchedule api

Kubeflow also allows it through using APICronSchedule which we currently use and has StartTime and EndTime attributes.

Tasks

• Document how to create new version of 1 or more CRDs
• Add kubebuilder to .tool-versions (particularly if we need it for upgrading CRD versions)?
• Update docs (e.g. RunSchedule and RunConfiguration examples)
• Pass startTime & endTime to VAI & KFP apis if set
• Create conversion code for v1alpha5&6 to handle startTime and endTime