PURPOSE

As new features are about to land in survey, notably live interactions [1]
and new survey building [2] performing a pre cleaning is necessary. In this
PR we clean survey models by: removing unnecessary fields, cleaning some code
and finally renaming models.

SPECIFICATIONS

Add a new demo survey about a quiz: a survey with scoring but no certificate.
Have almost all possible combinations of questions and options (notably choices
to have a scoring) and answer lines in order to be able to, notably, debug
the statistics / result page.

LINKS

[0] Related to Task ID 2061901 (survey models cleaning and preparation)
[1] Task ID 1972640 (live interactions)
[2] Task ID 2119587 (new frontend for building surveys)

PR #40765