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')

Userland/Libraries/LibWeb/HTML/WindowProxy.cpp

@@ -241,7 +241,7 @@ JS::ThrowCompletionOr<JS::MarkedVector<JS::Value>> WindowProxy::internal_own_pro
     // 5. Repeat while index < maxProperties,
     for (size_t i = 0; i < max_properties; ++i) {
         // 1. Add ! ToString(index) as the last element of keys.
-        keys.append(JS::PrimitiveString::create(vm, DeprecatedString::number(i)));
+        keys.append(JS::PrimitiveString::create(vm, ByteString::number(i)));
 
         // 2. Increment index by 1.
     }