The return type of ktesting.NewTestContext is now a TContext. Code
which combined it WithCancel often didn't compile anymore (cannot overwrite
ktesting.TContext with context.Context). This is a good thing because all of
that code can be simplified to let ktesting handle the cancelation.
The new TContext interface combines a normal context and the testing interface,
then adds some helper methods. The context gets canceled when the test is done,
but that can also be requested earlier via Cancel.
The intended usage is to pass a single `tCtx ktesting.TContext` parameter
around in all helper functions that get called by a unit or integration test.
Logging is also more useful: Log[f] and Fatal[f] output is prefixed with
"[FATAL] ERROR: " to make it stand out more from regular log output.
If this approach turns out to be useful, it could be extended further (for
example, with a per-test timeout) and might get moved to a staging repository
to enable usage of it in other staging repositories.
To allow other implementations besides testing.T and testing.B, a custom
ktesting.TB interface gets defined with the methods expected from the
actual implementation. One such implementation can be ginkgo.GinkgoT().
The upstream ktesting has to be very flexible to accommodate different ways of
using it. In Kubernetes, we can be opinionated and make certain choices, like
using klog flags, and only those.
