✨ Add support for OCI image volumes instead of init containers (KEP-4639)

[andersonshatch]

KEP-4639 introduced OCI image volume support, allowing you to mount a container as a volume.
This is essentially what the operator does, but the init container first has to copy its contents to a volume mounted on to the application container.
With Kubernetes 1.35, this feature got GA'd, and adding this support means we no longer need to have an init container.
This helps for the larger images we mount, as the copy is no longer necessary.

(Unscientific) Testing locally, this cuts out the following time where the init container runs to copy

Language	Run 1	Run 2	Run 3	Run 4	Run 5
.NET Core	5s	1s	1s	1s	1s
Flex	15s	9s	16s	12s	10s
Java	0s	0s	1s	0s	0s
Node.js	6s	7s	5s	5s	7s
PHP	0s	1s	0s	1s	1s
Python	2s	0s	3s	0s	1s

It's opt-in since we must maintain backwards compatibility.

In testing, it seems no k8s runtime version currently supports the sub path option, so we have to mount the full image as a volume, rather than just the /contrast directory.

We may want to mark this as experimental, as it's new, and maybe we find out we want to maintain init containers for some other reason down the line?
Maybe we also want to collect telemetry?

[andersonshatch]

Added some Claude/Copilot written tests, new territory for me. Not sure if these are any good.
I suppose 1.35 should also be added to the manifest/integration testing matrix.