Collecting issues here related to missing GC APIs in mono

#35960
#37950
#42883

Required for net 8.0:

• AddMemoryPressure Calls into runtime, but does not do anything: https://github.com/dotnet/runtime/blob/main/src/mono/mono/metadata/sgen-mono.c#L2872

Not Required for net 8.0, but for full coreclr parity

Right now these GC APIs throw NotSupportedException:

• GCSettings.LatencyMode (allows only LatencyMode.Batch, Aggressive throws not supported; implementable in Mono?)
• GC.TryStartNoGCRegion() (throws not supported)
• GC.RegisterForFullGCNotification() (throws not supported)
• GetTotalPauseDuration() (throws not supported)
• GetConfigurationVariables (it's ok if this returns different keys/values for mono)

This was implemented but the test is still disabled because were issues to be investigated, seehttps://github.com/mono/mono/issues/15236. There are also more fields to be implemented: https://learn.microsoft.com/en-us/dotnet/api/system.gcmemoryinfo?source=recommendations&view=net-7.0

• GC.GetGCMemoryInfo