Merge pull request #7242 from daxian-dbw/exp

Add support to experimental features

RFC: https://github.com/PowerShell/PowerShell-RFC/pull/114

Goals:

Allow experimental features to be declared by PowerShell engine and modules.
Allow experimental features to be enabled via powershell.config.json
Allow Function, Cmdlet, parameters and parameter sets to be shown to the user or hiden from the user depending on whether the associated experimetnal feature is on or off.
Allow discover experimental features using cmdlet Get-ExperimentalFeature

src/System.Management.Automation/engine/remoting/common/PSETWTracer.cs

@@ -159,6 +159,10 @@ namespace System.Management.Automation.Internal
         Settings = 0x1F04,
         Engine_Trace = 0x1F06,
 
+        // Experimental Features
+        ExperimentalFeature_InvalidName = 0x3001,
+        ExperimentalFeature_ReadConfig_Error = 0x3002,
+
         // Scheduled Jobs
         ScheduledJob_Start = 0xD001,
         ScheduledJob_Complete = 0xD002,
@@ -232,6 +236,7 @@ namespace System.Management.Automation.Internal
         ProviderStart = 0x68,
         ProviderStop = 0x69,
         ExecutePipeline = 0x6A,
+        ExperimentalFeature = 0x6B,
         ScheduledJob = 0x6E,
         NamedPipe = 0x6F,
         ISEOperation = 0x78