Replace cherrypy with cheroot

[waghanza]

Hi @defnull,

This PR completely remove cherrypy usage.

It :

• [x] Removes cherrypy as backend server (code is removed, but using it as backend server will start cheroot) ℹ️ Not sure there is a lot of people using cherrypy < 9 , btw this version this backend could not be used with cherrypy >= 9
• [x] Updates doc link

⚠️ I'm not sure cheroot includes any GZip feature

Regards,

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Closes #934 Closes #975 Closes #426