bi_sql_editor: add support for group operators

this commit allows specifying the group operator for each field. This functionality was originally included in a seperate module "bi_sql_editor_aggregate" in version 12.

bi_sql_editor/views/view_bi_sql_view.xml

@@ -149,6 +149,11 @@ License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
                                     <field name="name" />
                                     <field name="sql_type" />
                                     <field name="field_description" />
+                                    <field
+                                        name='group_operator'
+                                        attrs="{
+                                        'invisible': ['!', ('ttype', 'in', ('float', 'integer'))]}"
+                                    />
                                     <field
                                         name="ttype"
                                         attrs="{