A previous commit makes the graph view render only the finer interval
option for each date/datetime field.
The fact is that in the control panel, different options can be selected
in any order along with other groupbys. This can lead to situations like
'Foo > Date: Day > Bar > Date: Month'
and becomes unreadable.
For that reason we choose to regroup and order options. For the previous
situation, this leads to the following global groupby
'Foo > Date: Month > Date: Day > Bar'.
Our choice also make more sense in a list view for instance.
Task ID: 2198846
closesodoo/odoo#46269
X-original-commit: 59afc869233165e21ef94f485b91d33ac4543b24
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>