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/Utilities/stat.cpp

@@ -73,7 +73,7 @@ static ErrorOr<int> stat(StringView file, bool should_follow_links)
     outln(")");
 
     auto print_time = [](timespec t) {
-        outln("{}.{:09}", Core::DateTime::from_timestamp(t.tv_sec).to_deprecated_string(), t.tv_nsec);
+        outln("{}.{:09}", Core::DateTime::from_timestamp(t.tv_sec).to_byte_string(), t.tv_nsec);
     };
 
     out("Accessed: ");