feat: Support running nats-leaf in a Kubernetes native sidecar container

[joonas]

Per the blog post introducing "native" sidecar containers and the sidecar containers documentation, the pattern has reached a state (in this case, beta) where we should be able to leverage it if we're running in a relatively new (v1.29, which was released on Wednesday, December 13, 2023) version of Kubernetes.

This has some nice benefits such as obviating the need for #86 as the sidecars will start ahead of the wasmCloud host, and as of v1.30 sidecars are also counted towards pod resource utilization, so there aren't any real downsides to the approach.