Centralize logging for health indicator failures

[josephabonasara]

Centralize logging for health indicator failures.

• Add HealthLogger class to centralize logging for health indicator failures.
• Remove logExceptionIfPresent method from AbstractHealthIndicator and AbstractReactiveHealthIndicator.
• Update AbstractHealthIndicator and AbstractReactiveHealthIndicator to use HealthLogger.logExceptionIfPresent.
• Add exception field to Health class and update Builder class to set the exception field.
• Add getException method to Health class to retrieve the exception.
• Update HealthEndpointSupport to use HealthLogger.logExceptionIfPresent.
• Add HealthLoggerTests class to test the HealthLogger class.

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[philwebb]

Thanks for the pull-request, but I'm afraid this wasn't quite what I had in mind. I should have put the pending-design-work label on that issue to make it clearer that we aren't ready for contributions just yet.

I think what we want to do is remove the logging entirely from the *HealthIndicator classes and instead make the calling code responsible for doing the logging. We're going to need a bit more time to really think about the design and the impact of such a change. I don't think we'll be really ready to start on this one until the new year.

Thanks anyway for your contribution and I'm sorry about any wasted effort.