Do not allow calls to `html_escape`, `url_encode` from top-level namespace (`Object`)

It was found in !132834 (comment 1611890878) that ERB::Util is included at the top-level, via https://github.com/jgarber/redcloth/blob/master/lib/redcloth.rb#L40-L45

Proposal

Make a cop to ban calls to :


## bad, unless in HAML or ERB template
u
h
url_encode
html_escape

## good
ERB::Util.u
ERB::Util.h
ERB::Util.url_encode
ERB::Util.html_escape

See also this Draft MR to fix majority of places !134950 (closed)

Links:

Edited by Thong Kuah