[WIP] Make issue assigned filters more uniform across group and project [Can be updated]

Created by: cirosantilli

This PR makes the Assigned to me / created by me / everyone's issue filter more uniform between project, dashboard and group issues.

The only UI change is that for the dashboard and group, the order changed from:

• assigned to me
• created by me
• everyone's

to:

• everyone's
• assigned to me
• created by me

which matches the order under projects. Those two should have the same order: it makes the UI more uniform.

Note that the default values for those attributes is different between views and has not been changed: for dashboard it is assigned to me, for groups depends on signed in or not, and for project issues it is always everyone's.

The greater uniformity also allowed a large factorization.

Implementation notes:

• removed the .scope-filter class which is not used anywhere
• removed the unused entity argument to facilitate polymorphism