cubicweb #6206636 system_source.do_fti don't fully control full-text indexatoin [validation pending]

during migration, one may want to do 'repo.system_source.do_fti = False' to deactivate full-text indexation, but this is currently ignored when some relation with "full-text container" set are modified.

prioritynormal
typebug
done in3.20.10
load1.000
load left0.000
closed by#1ab79c435fae consider .do_fti flag in index_entity method
patchconsider .do_fti flag in index_entity method [applied]