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/Fetch/Infrastructure/HTTP/Requests.cpp

@@ -196,7 +196,7 @@ ErrorOr<String> Request::serialize_origin() const
         return "null"_string;
 
     // 2. Return request’s origin, serialized.
-    return String::from_deprecated_string(m_origin.get<HTML::Origin>().serialize());
+    return String::from_byte_string(m_origin.get<HTML::Origin>().serialize());
 }
 
 // https://fetch.spec.whatwg.org/#byte-serializing-a-request-origin