cubicweb #750091 rql rewriter: support for has_*_permission in entity 'read' permission [open]

there is already some support but it doesn't seems to work. We should benefit from this to optimize cases like :

ETypeA has some read permission ETypeB has read permission 'B linked_to A, U has_read_permission A'

user query 'B linked_to A': we should only insert security for A.