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/SVG/SVGScriptElement.cpp

@@ -59,7 +59,7 @@ void SVGScriptElement::process_the_script_element()
     auto& settings_object = document().relevant_settings_object();
     auto base_url = document().base_url();
 
-    m_script = HTML::ClassicScript::create(m_document->url().to_deprecated_string(), inline_script, settings_object, base_url, m_source_line_number);
+    m_script = HTML::ClassicScript::create(m_document->url().to_byte_string(), inline_script, settings_object, base_url, m_source_line_number);
     (void)m_script->run();
 }