Hyper.html should take a Blaze.Html type as input

I propose that Hyper.html takes a Blaze.Html type as input.
This would mean that Hyper has to decide which HTML standard to use, but the current mixing of standards is certainly not better.

The issue names Hyper.html and Blaze.Html but no files or tests. Start by locating the Hyper.html entry point and checking how HTML values are currently represented and which standard they use. Done means Hyper.html accepts Blaze.Html consistently, with relevant tests updated or added.

Written by the indexing model from the issue text.