LibURL+Everywhere: Only percent decode URL paths when actually needed

Web specs do not return through javascript percent decoded URL path
components - but we were doing this in a number of places due to the
default behaviour of URL::serialize_path.

Since percent encoded URL paths may not contain valid UTF-8 - this was
resulting in us crashing in these places.

For example - on an HTMLAnchorElement when retrieving the pathname for
the URL of:

http://ladybird.org/foo%C2%91%91

To fix this make the URL class only return the percent encoded
serialized path, matching the URL spec. When the decoded path is
required instead explicitly call URL::percent_decode.

This fixes a crash running WPT URL tests for the anchor element on:

https://wpt.live/url/a-element.html

Userland/Libraries/LibWebSocket/ConnectionInfo.cpp

@@ -26,7 +26,7 @@ ByteString ConnectionInfo::resource_name() const
     // The "resource-name" can be constructed by concatenating the following:
     StringBuilder builder;
     // "/" if the path component is empty
-    auto path = m_url.serialize_path();
+    auto path = URL::percent_decode(m_url.serialize_path());
     if (path.is_empty())
         builder.append('/');
     // The path component