Everywhere: Add deprecated_ prefix to JsonValue::to_byte_string

`JsonValue::to_byte_string` has peculiar type-erasure semantics which is
not usually intended. Unfortunately, it also has a very stereotypical
name which does not warn about unexpected behavior. So let's prefix it
with `deprecated_` to make new code use `as_string` if it just wants to
get string value or `serialized<StringBuilder>` if it needs to do proper
serialization.

Userland/Utilities/lsirq.cpp

@@ -42,7 +42,7 @@ ErrorOr<int> serenity_main(Main::Arguments)
         out("{:>4}: ", interrupt);
 
         for (size_t i = 0; i < cpu_count; ++i)
-            out("{:>10}", call_counts[i].to_byte_string());
+            out("{:>10}", call_counts[i].as_integer<u64>());
 
         outln("  {:10}  {:30}", controller, purpose);
     });