feat: set service v0

[tedim52]

Description

Adds set_service instruction which can be used to override the service config of a service added earlier in the plan. This can be really useful for two cases:

1. A user wants to set a specific image (or other config) for a service in a package but the package author has not made the image configurable. This can be done by appending set_service to the plan.
   ex.

postgres = import_module("github.com/kurtosis-tech/postgres-package/main.star")

def run(plan, args):
    postgres.run(plan)
    plan.set_service(name="postgres", config=ServiceConfig(image="postgres:bullseye"))

2. A user wants to swap out the image (or other config) of a service running in an enclave. This can be done by appending set_service to the plan and enclave editing.
   ex.
   https://www.loom.com/share/f88d0f5555dd49b0aeabc55c5ed41d43

This instruction has some functionality missing such as overriding ports, env vars, and cmd/entrypoint as these require special handling of future references and handling consecutive set service instructions properly but functionality can be added iteratively in future PRs.

Is this change user facing?

YES

References:

#2057

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