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/Applications/SystemMonitor/ThreadStackWidget.cpp

@@ -49,7 +49,7 @@ public:
         auto& symbol = m_symbols[model_index.row()];
         switch (model_index.column()) {
         case Column::Address:
-            return DeprecatedString::formatted("{:p}", symbol.address);
+            return ByteString::formatted("{:p}", symbol.address);
         case Column::Object:
             return symbol.object;
         case Column::Symbol: