Use case: if both ACM and Kubevirt plugins are enabled, we want ACM plugin to load fully prior to loading Kubevirt plugin. However, if ACM plugin is absent but Kubevirt plugin is enabled, we still want the Kubevirt plugin to load as usual.

Therefore, we would like to support plugins declaring optional dependencies on other plugins.

The current implementation supports non-optional plugin dependencies only.

We need to modify unavailablePluginNames handling - skip any optional-but-required plugins.

AC: Add an optional dependency for a dynamic plugin to specify a dependent dynamic plugin.