[receiver/k8sobjects] Fix memory leak caused by pull mode's interval ticker

[crobert-1]

Description:

The k8sobjects receiver was starting a ticker when in pull mode, that would tick every set interval. This ticker needs to be stopped during shutdown, so I added functionality to cancel the context during shutdown, properly stopping the ticker.

The original intention here was to add goleak, but due to a bug in internal/k8stest it's failing on the end to end test. This change still fixes a bug, so I believe it's worth merging even without goleak at this point. Note that this change does reduce the number and frequency of goleak failures.

Testing:
All existing tests are passing.

[crobert-1]

I'll investigate failing goleak test and mark as Ready to Review when I've resolved it.

[TylerHelmuth]

I wonder how related this is to #31644

[crobert-1]

I wonder how related this is to #31644

I suspect this is actually frequency of #31047, since the only test that's failing is using k8stest, and the leaked goroutines have the same stack.

[crobert-1]

I've updated the issue description. goleak is still failing on the end to end test due to a bug in internal/k8stest. I believe this is still worth merging to fix the memory leak detected, even if goleak isn't included.