* 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