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/ProcessFileDescriptorMapWidget.cpp

@@ -53,7 +53,7 @@ void ProcessFileDescriptorMapWidget::set_pid(pid_t pid)
     if (m_pid == pid)
         return;
     m_pid = pid;
-    m_model->set_json_path(DeprecatedString::formatted("/proc/{}/fds", m_pid));
+    m_model->set_json_path(ByteString::formatted("/proc/{}/fds", m_pid));
 }
 
 }