Improve renovate config for Istio

Currently the renovate config can lead to issues as it will open MRs to certain updates before the images are actually ready. This is primarily due to the values file format of istio, which uses a base "hub" for all images.

We should investigate and update the renovate config to track all 3 necessary images separately (and properly) to make it clear when updates are ready to be worked:

• istio pilot
• istio proxyv2
• istio install-cni

One of the primary issues currently is that the regex match strings in https://repo1.dso.mil/platform-one/big-bang/apps/core/istio-controlplane/-/blob/main/renovate.json are all the same for each image. We likely will need unique regex matches to make this properly work.

Potentially helpful note: The install cni image has a separate values section which we can track directly. We might be able to also add values for the pilot and proxy images to track them similarly.