Add support for K8s native sidecars (restartable init containers)

K8s v1.28 added support for native sidecars. This introduces restartable init containers, ie. init containers that keep running along with the main ones.

The changes resource request calculations. A helper method in the K8s codebase is available for resource calculations. However, this seems to be too complicated and inefficient.

Our options are:
1. Change our existing code in the shim and update our unit tests.
2. Re-use the GetPodResources() function from K8s.

If we keep our own code, I recommend that we create unit tests that perform comparisons between the two.