[FIX] survey: display the absolute counter in time limited survey

Before this commit:
Let's consider the following two scenarios while answering time limited survey:

1) attendee's system clock is de-synchronized compared to the real time
2) Odoo server clock is de-synchronized compared to the real time

In any/both of the above cases, it will lead to a wrong timer display, and will
confuse the user and/or make him fail the test because he will think he still has
more time to submit when he does not.

With this commit:
To fix this, we simply get the offset of server UTC time and moment time, and apply
the offset while calculating the time remaining.

Task-2612972

closes odoo/odoo#75814

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>