Allow the user to opt-out of anonymous access restrictions for /health

By default, when /health is accessed anonymously, the details are
stripped, i.e. the response will only indicate UP or DOWN. Furthermore
the response is cached for a configurable period to prevent a denial
of service attack.

This commit adds a configuration property,
endpoints.health.restrict-anonymous-access, that can be set to false
to allow full anonymous access to /health. When full access is
allowed, the details will be included in the response and the response
will not be cached.

Closes gh-1977