Makes Start-Trace escape file paths correctly (#3863)

Start-Trace neglects qualifying arguments to the -o and -pf command line
switches, causing logman (and subsequently Start-Trace) to exit with
0x80070057 and return:

Error:
The argument is incorrect.

Whenever arguments to either -ProviderFilePath or -OutputFilePath
contain spaces because Start-Trace doesn't escape the path in any way.

This commit moves basic input validation for output file paths to the
ProviderFilePath and OutputFilePath parameter definitions, and adds text
qualifiers (double-quotes) around input arguments

src/Modules/Windows-Core+Full/PSDiagnostics/PSDiagnostics.psm1

@@ -27,9 +27,11 @@ function Start-Trace
     [string]
     $SessionName,
     [Parameter(Position=1)]
+    [ValidateNotNullOrEmpty()]
     [string]
     $OutputFilePath,
     [Parameter(Position=2)]
+    [ValidateNotNullOrEmpty()]
     [string]
     $ProviderFilePath,
     [Parameter()]
@@ -63,12 +65,12 @@ function Start-Trace
 
         if ($null -ne $OutputFilePath)
         {
-            $executestring += " -o $OutputFilePath"
+            $executestring += " -o ""$OutputFilePath"""
         }
 
         if ($null -ne $ProviderFilePath)
         {
-            $executestring += " -pf $ProviderFilePath"
+            $executestring += " -pf ""$ProviderFilePath"""
         }
 
         if ($null -ne $Format)