Everywhere: Rename {Deprecated => Byte}String

This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).

This commit is auto-generated:
  $ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
    Meta Ports Ladybird Tests Kernel)
  $ perl -pie 's/\bDeprecatedString\b/ByteString/g;
    s/deprecated_string/byte_string/g' $xs
  $ clang-format --style=file -i \
    $(git diff --name-only | grep \.cpp\|\.h)
  $ gn format $(git ls-files '*.gn' '*.gni')

AK/Error.h

@@ -43,10 +43,10 @@ public:
     }
     static Error from_string_view(StringView string_literal) { return Error(string_literal); }
 
-    template<OneOf<DeprecatedString, DeprecatedFlyString, String, FlyString> T>
+    template<OneOf<ByteString, DeprecatedFlyString, String, FlyString> T>
     static Error from_string_view(T)
     {
-        // `Error::from_string_view(DeprecatedString::formatted(...))` is a somewhat common mistake, which leads to a UAF situation.
+        // `Error::from_string_view(ByteString::formatted(...))` is a somewhat common mistake, which leads to a UAF situation.
         // If your string outlives this error and _isn't_ a temporary being passed to this function, explicitly call .view() on it to resolve to the StringView overload.
         static_assert(DependentFalse<T>, "Error::from_string_view(String) is almost always a use-after-free");
         VERIFY_NOT_REACHED();