* Refactor jobs from HostedServices into BackgroundJobs
* Clean up generics and DI setup
* Add RecurringBackgroundJob Unit Tests
* Add ServiceCollection helper
* Add Obsolete attributes
* Add Notification Classes
* Add UnitTests for RecurringBackgroundJob HostedService
* Add NotificationEvents
* Add state to notifications
* Update UnitTests
* Add Obsolete Attributes to old hosted service classes
* Updated xmldoc in IRecurringBackgroundJob.cs
* Update Obsolete attribute messages to indicate classes will be removed in Umbraco 14
(cherry picked from commit c30ffa9ac3)
* Refactors the logic for calculating the first run time for a recurring task for easier re-use by similar hostservices.
* Renamed method to match wider usage.
* Separate legacy scope provider interface and explicitly implement.
* Don't rely on legacy scope provider for existing tests.
* Assert correct type returned when using legacy scope provider.
* Filesystem based MainDomLock & extract interface for MainDomKey generation (#12037)
* Extract MainDomKey generation to its own class to ease customization.
Also add discriminator config value to GlobalSettings for advanced users.
Prevents a mandatory custom implementation, should be good enough for
the vast majority of use cases.
* Prevent duplicate runs of ScheduledPublishing during slot swap.
* Add filesystem based MainDomLock
(cherry picked from commit 860c8e8ae2)
# Conflicts:
# src/Umbraco.Infrastructure/Runtime/SqlMainDomLock.cs
* Remove obsolete constructors from ScheduledPublishing & SqlMainDomLock
* FileSystemMainDomLock promoted to default fallback for all platforms.
* Various fixes & improvements
