cubicweb #6694446 [tests] use predictable representation of rql queries [validation pending]

rql's as_string() isn't quite sure how to quote string constants. CubicWeb's tests should make sure to always use the same representation. See also https://www.logilab.org/ticket/1190507

prioritynormal
typebug
done in3.22.0
load1.000
load left0.000
closed by#97f6b3d655fc [test] use unicode for rql queries (7/7)
patch[test] use unicode for rql queries (1/7) [applied][test] use unicode for rql queries (7/7) [applied][test] use unicode for rql queries (6/7) [applied][test] use unicode for rql queries (5/7) [applied][test] use unicode for rql queries (4/7) [applied][test] use unicode for rql queries (3/7) [applied][test] use unicode for rql queries (2/7) [applied]