Steps to reproduce:

1. change system and admin's time zone to one with a different
date than UTC
2. enable multi-currency in the accounting module
3. add rates for the current date in local time zone and UTC
4. go to settings > currencies
5. the rate for the UTC date is displayed

To fix this, we should use a time zone aware field in `res_currency`.

opw-2945108

closes odoo/odoo#101640

X-original-commit: 2f1d8d6d
Signed-off-by: William André (wan) <wan@odoo.com>
Signed-off-by: Khanalizadeh Ahmad (khah) <khah@odoo.com>