Computing the recurrences of a task repeating every X months until a
certain date generates too much dates

Steps to reproduce:
1. Install Project
2. Go to Settings > Project > Tasks Management and enable Recurring
   Tasks
3. Open any project in the Project app and create a new task then edit
   it
4. Enable the Recurrent field of the task
5. In the Recurrence tab, edit:
   - Repeat Every: 6 Months
   - Until: End Date: one year from now
6. The recurrence message says there are 11 tasks but there should only
   be 2

Solution:
Generate the recurrences until the `repeat_until` date is reached if the
`repeat_type` is 'until', otherwise generate as much recurrences as the
count
Also relax the constraint on the `repeat_day` and `repeat_until` to not
raise an error if `repeat_until` is the last day of the month

Problem:
The recurrence of a task with `repeat_unit` month and `repeat_interval`
different than 1 with a `repeat_type` until creates too much tasks,
exceeding the `repeat_until`

opw-3076593

closes odoo/odoo#107817

X-original-commit: f94dbfe0
Signed-off-by: Laurent Stukkens (ltu) <ltu@odoo.com>
Signed-off-by: Guillaume Merlin (megu) <megu@odoo.com>