Add java.time to list of allowed reflective accesses

[wilcoxjay]

Discovered from a student reporting spurious --checks warning about fast cloning and ClientWorker:

Objects cannot be fast-cloned. Check that they don't contain lambdas or other non-standard fields. This error could also occur due to the use of a data structure the fast-cloning library does not yet support.
- class dslabs.framework.testing.ClientWorker ...

Tracked it down by unswallowing the underlying exception to discover:

java.lang.reflect.InaccessibleObjectException: Unable to make field private static final long java.time.Instant.MIN_SECOND accessible: module java.base does not "opens java.time" to unnamed module.

This pointed to an "illegal" reflective access.

Adding another --add-opens fixes it, but we need to add it in three places:

• staff facing IntelliJ run configuration
• student facing IntelliJ run configuration
• (student-facing) run-tests.py

I believe this was introduced in the recent refactor of ClientWorker to support better timing information, using java.time.Instant as a field, which we had apparently never used in dslabs before (or at least not in a place that the cloning library needed to touch).

There is a separate question of why we are even trying to clone that Instant (either it's a run test, in which case we shouldn't be cloning nodes, or it's a search test, in which case we shouldn't be looking at the clock at all), but I'm ignoring that for now.