cubicweb #5456750 skip spa2rql when fyzz is not available [validation pending]

fyzz does not currently install properly in some cases (e.g. within a virtualenv) so that it may not be available to all development environment. spa2rql tests could be skipped (instead of failing) when fyzz is not available.

prioritynormal
typeenhancement
done in3.21.0
load0.100
load left0.000
closed by#f3dec653a27d [test] Skip spa2rql tests when fyzz is not available
patch[test] Skip spa2rql tests when fyzz is not available [applied]