Add JustAfterEach

[lwr20]

What this PR does / why we need it:

In the kubernetes end to end tests (which use Ginkgo), the structure is that there is a general framework and then specific test cases. Both have BeforeEach and AfterEach statements and the execution order is

Framework BeforeEach
  Test BeforeEach
    Test runs
  Test AfterEach
Framework AfterEach.

Quite often, the Test's BeforeEach sets up some infrastructure required for the test and the AfterEach tears it down.

However, if a test fails, we want to collect diags as close to the failure as possible. We could find and modify all the innermost AfterEach's and add diags to them all. But it would be much nicer to be able to have a JustAfterEach in the Framework that all the tests use that works in a similar way to JustBeforeEach.

This problem was mentioned in kubernetes/kubernetes#34318, although that wasn't explicitly about this.

[fasaxc]

LGTM; probably will need docs updates to upstream