For Maven declared_license normalization, also consider all text at once as well as POM XML comments

### Description
The licenses tags in a Maven POM are normalized using license tags in the XML but we ignore XML-wide comments. It si common in POMs to have a license in an XML top-level comment. Licenses in POM XML comments would be caught by the plain text detection alright but we want then in the package licenses instead.

We should enhance this by:
1. Looking at the text made of lines of (name, url, comments)
2. Considering the XML comments in the package normalization too
3