Normalizer should transform certain parts of IRIs to their lower-cased form

See https://datatracker.ietf.org/doc/html/rfc2616#section-3.2.3 :
* Comparisons of host names MUST be case-insensitive;
* Comparisons of scheme names MUST be case-insensitive;

Start by locating the IRI normalizer and compare its handling of scheme names and host names with RFC 2616 section 3.2.3. Done means those two components are normalized to lower case while the issue's stated case-insensitive comparison requirements are satisfied.

Written by the indexing model from the issue text.