make it look more like our other modules

sphinx 0.6 switched templates to jinja2, which has an incompatible
syntax for macros.  2009, here we come!
Closes #113086.

This is very useful for test

This is much more readable

We need this for set comparison implemented in 2a175b352c78

The old code did:
* forge a string
* eval it as a lamba
* monkey patch classes with the result

We may just drop the logic looping on multiple class by computing class name
dynamically. But this have a different behavior for subclass.

Use set instead of list for domains. This remove some N² complexity. Simplify
the visite_relation code to:

* avoid computation duplication,
* compare string instead of Yams object,
* take advantage of set.

fix Referencable.get_type crash when no solution given and 'is IN(ET1, ET2..) is used. Closes #81865

668:b2e231cbd9da introduces unrelated changes that 1. break tests, 2. make rql>0.30.1 incompatible with cw < 3.13.10