[FIX] web: can't edit subscription with end date beyond 200 years in the future

-Import a subscription with end date beyond 200 in the future (ex: 2500-01-01).
-Open the subscription and click the Edit button.

Before this commit:

A stacktrace appears indicating that a date is not valid. It's not possible to
edit the subscription.

After this commit:

The maxDate of the date picker has been increased to 31/12/9999, allowing the
user to edit subscriptions whose end date is that far in the future.

A test `toggle datepicker far in the future` for this case has been created.

closes odoo/odoo#38527

Opw: 2079696
X-original-commit: 32b6131c04fef7a542a0ccbdb924d177627bfe38
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>