AK+Everywhere: Rename String to DeprecatedString

We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)

Userland/Libraries/LibCrypto/Hash/HashManager.h

@@ -192,10 +192,10 @@ public:
     }
 
 #ifndef KERNEL
-    virtual String class_name() const override
+    virtual DeprecatedString class_name() const override
     {
         return m_algorithm.visit(
-            [&](Empty const&) -> String { return "UninitializedHashManager"; },
+            [&](Empty const&) -> DeprecatedString { return "UninitializedHashManager"; },
             [&](auto const& hash) { return hash.class_name(); });
     }
 #endif