Remove use of DateTime.Now in ValidationAppSI and DefaultEformidlingService

[tjololo]

Description of the bug

In all other places where we need to get the current time we use DateTime.UtcNow. In ValidationAppSI and DefaultEFormidlingService we use DateTIme.Now. I the correct way is to use UtcNow as that will remove the connection to the timesone where the code is executed.
If UtcNow is wrong we at least need to be consistent across our codebase

Steps To Reproduce

1. Create an app submit a for
2. See Timestampe in the instance validated block. This has timezone matching the computers timezone
3. Other timestamps are in utc

Additional Information

No response