feat: add --logs-collector-enabled flag to kubernetes create Fixes #485

[yuvarajrece]

Summary

Fixes #485

Adds a --logs-collector-enabled flag to civo kubernetes create,
allowing users to control whether the logs collector is installed on a
new cluster.

• If the flag is explicitly set, that value is always respected
  regardless of node size.
• If not explicitly set, the logs collector is automatically disabled on
  standard small/xsmall nodes (g4s.kube.small, g4s.kube.xsmall) to
  save node resources, and an informational message is printed:
  "Logs collector not installed by default to save resource on small and
  xsmall standard nodes. If you wish to enable logs collector create the
  cluster with LogsCollectorEnable set to true"
• For all other node sizes, the value is left unset by default, so the
  API's own default applies.

Depends on civo/civogo#<PR_NUMBER_HERE> for the underlying
LogsCollectorEnabled field on KubernetesClusterConfig — needs to be
merged and released before this PR can build against a real civogo
version bump (currently uses a local replace only for testing, removed
before submission).

Testing

Added unit tests in utility/kubernetes_test.go covering node-size
detection and the enable/disable resolution logic (explicit flag,
auto-disable on standard small/xsmall, default-deferred on other sizes,
and confirming non-standard tiers like performance/RAM/CPU-optimized are
not affected).