Refactor logic for notice files

Move things around so that we don't need to check whether
we're in the "split license file mode" over and over, and
some other moves to improve readability.

Also rename the html_or_xml variables to the correct name
given the branch of the conditional we're in, to make it
easier to grok.

Bug: 118089975
Test: diff notice files for blueline before and after
Change-Id: I00fcdce31503c543c6c0ab6901531c54c9705617