[feature request] Sidecarset support guarantees the order of sidecar

[zmberg]

What would you like to be added:
Sidecarset determines the sidecar order based on the sidecar name alphabetical order.

There are some sidecars that must be first, such as kube-agent, which cannot be guaranteed by name alone. Therefore, we would like to have a way to configure Admin to guarantee that kube-agent will be injected first.

Why is this needed: