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/HTML/Scripting/WindowEnvironmentSettingsObject.h

@@ -21,7 +21,7 @@ public:
     virtual ~WindowEnvironmentSettingsObject() override;
 
     virtual JS::GCPtr<DOM::Document> responsible_document() override;
-    virtual DeprecatedString api_url_character_encoding() override;
+    virtual ByteString api_url_character_encoding() override;
     virtual AK::URL api_base_url() override;
     virtual Origin origin() override;
     virtual PolicyContainer policy_container() override;