A path redirect may contain any and all parts of a url which have different
escaping rules for each part. This commit tries to escape each part correctly
by splitting the string into three chunks - path (which may also include a host),
query and fragment; then it applies the correct escape pattern to each part.

Whilst using `URI.parse` would be better, unfortunately the possible presence
of %{name} parameters in the path redirect string prevents us from using it so
we have to use a regular expression instead.

Fixes #13110.