feat: Add kubernetes agent deployment target

[tleed5]

Background

To fully be able to manage the Kubernetes agent in an automated environment we need to add a new deployment target resource for it.

fixes #637
Internal Story SC-77238
Depends on OctopusDeploy/go-octopusdeploy#248 , OctopusDeploy/helm-charts#148 and OctopusDeploy/OctopusTentacle#927

Result

• Added new deployment target resource octopusdeploy_kubernetes_agent_deployment_target
• Added run configuration and instructions for debugging the provider

Example usage:

resource "octopusdeploy_kubernetes_agent_deployment_target" "agent" {
  name         = "my-agent"
  environments = [octopusdeploy_environment.development_environment.id]
  roles        = ["role-1", "role-2"]
}

data "octopusdeploy_kubernetes_agent_deployment_targets" "all" {}

[tleed5]

Using this in combination with a replace_triggered_by lifecycle hook on the helm release resource will allow the agent to "re-register" (It actually a re-install) so you could rotate the certificate and subscription IDs if you wanted to

[APErebus]

It looks good to me! I'm not super confident on reviewing terraform so I'm going to give an approve, but might be worth getting 👀 from someone who's more familiar

[zentron]

I did have some reservations about the new octopusdeploy_tentacle_certificate resource, but after looking at what we would need to do with the built-in cert I think the trade off for simplicity is ok, particularly given the reversable nature of this addition.

I haven't flagged as request changes but have included a comment to add some more notes to the documentation template. Feel free to merge once this is done.

[zentron]

Nice one. Ill include the VsCode docs details in a follow up

[zentron]

Not sure where the template for this file is, but it would be worth outlining that this certificate is self-signed and should not be used for other purposes.
Feel free to adjust the below as necessary for phrasing.

##Octopus certificates
The X.509 certificates generated are self-signed, 2048-bit private keys and intended for use [only between Octopus Server and Tentacle](https://octopus.com/docs/security/octopus-tentacle-communication#Octopus-Tentaclecommunication-Octopuscertificates) communications. There is an insightful discussion of [why Octopus uses self-signed certificates](https://octopus.com/blog/why-self-signed-certificates) by default.

Instead of generating a new certificate through this resource you can use an existing certificate and simply reference the appropriate thumbprint when registering the target.

### State Persistence
This resource that is generated will be stored in the state file and cannot be retrieved later from the external Octopus Server or Tentacle.