cubicweb-email #9943931 extract the EmailValueGenerator in a testutils modules [validation pending]

so it can be used for generative tests in cubes that depends on Email

prioritynormal
typeenhancement
done in1.12.0
load0.100
load left0.000
closed by#e762869b5bbb [tests] extract the EmailValueGenerator in a module (closes #9943931)
patch[tests] extract the EmailValueGenerator in a module (closes #9943931) [applied]