Improve scheduled jobs telemetry

Description

Telemetry visible in admin mode for each job:

• Duration, how long the job took to complete
• Server, on which server the job ran
• Improved status, added Cancelled to Succeeded and Failed
• Doubled paging size under the log tab

Telemtry in database/API:

• Logs if the job was started by the scheduler or manually (for troubleshooting purposes)
• Increase log size from 100 to 1,000 for each job
• Increase Message column from NVARCHAR(2048) to NVARCHAR(MAX)

Other relatated improvements:

• Execute job manually in admin should keep running on existing schedule (for example do not change time of day)
• Should be possible to define GUID on plug-in [ScheduledJobPlugin(GUID=...)] to make it possible to rename jobs but still keep the log
• IsStoppable is synched to the database on startup so that the job type does not have to be created every time to read this property