currently:

• ad-hoc inplace HealthCheck lambdas within ModuleManager startup method
• registered programmatically via HealthCheckRegistry#register...

expected:

• extract HealthCheck impl to separate class, taking ModuleManager as constructor parameter (itself exposing its state flags for liveness/readiness via getters)
• still registered programmatically as above, but possibly earlier in ModuleManagerImpl constructor, passing itself as reference
  • later on, this could be "auto-wired" after Guice integration for auto-discovery & injection within HealthChecks (MAGNOLIA-9247)