Cache regex instances in most cases (#27699)

Using static Regex functions that take in a pattern is bad because the pattern constantly needs to be re-parsed. With https://github.com/space-wizards/RobustToolbox/pull/5107, the engine has an analyzer to warn for this practice now.

This commit brings most of content up to snuff already, though some of the tricker code I left for somebody else.

Content.Shared/Preferences/HumanoidCharacterProfile.cs

@@ -26,6 +26,9 @@ namespace Content.Shared.Preferences
     [Serializable, NetSerializable]
     public sealed partial class HumanoidCharacterProfile : ICharacterProfile
     {
+        private static readonly Regex RestrictedNameRegex = new("[^A-Z,a-z,0-9, -]");
+        private static readonly Regex ICNameCaseRegex = new(@"^(?<word>\w)|\b(?<word>\w)(?=\w*$)");
+
         public const int MaxNameLength = 32;
         public const int MaxDescLength = 512;
 
@@ -418,15 +421,13 @@ namespace Content.Shared.Preferences
 
             if (configManager.GetCVar(CCVars.RestrictedNames))
             {
-                name = Regex.Replace(name, @"[^A-Z,a-z,0-9, -]", string.Empty);
+                name = RestrictedNameRegex.Replace(name, string.Empty);
             }
 
             if (configManager.GetCVar(CCVars.ICNameCase))
             {
                 // This regex replaces the first character of the first and last words of the name with their uppercase version
-                name = Regex.Replace(name,
-                @"^(?<word>\w)|\b(?<word>\w)(?=\w*$)",
-                m => m.Groups["word"].Value.ToUpper());
+                name = ICNameCaseRegex.Replace(name, m => m.Groups["word"].Value.ToUpper());
             }
 
             if (string.IsNullOrEmpty(name))