Simplify `MovieImporter.SingleSpaces`

src/BizHawk.Client.Common/movie/import/IMovieImport.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text.RegularExpressions;
 
 using BizHawk.Common;
 
@@ -122,22 +123,11 @@ namespace BizHawk.Client.Common
 			return str.Trim();
 		}
 
+		private static readonly Regex WhitespacePattern = new(@"\s+");
+
 		// Reduce all whitespace to single spaces.
 		protected static string SingleSpaces(string line)
-		{
+			=> WhitespacePattern.Replace(line, " ");
-			line = line.Replace("\t", " ");
-			line = line.Replace("\n", " ");
-			line = line.Replace("\r", " ");
-			line = line.Replace("\r\n", " ");
-			string prev;
-			do
-			{
-				prev = line;
-				line = line.Replace("  ", " ");
-			}
-			while (prev != line);
-			return line;
-		}
 
 		// Ends the string where a NULL character is found.
 		protected static string NullTerminated(string str)