This commit combines security autoconfigurations for
management endpoints and the rest of the application. By default,
if Spring Security is on the classpath, it turns on @EnableWebSecurity.
In the presence of another WebSecurityConfigurerAdapter this backs off
completely. A default AuthenticationManager is also provided with a user
and generated password. This can be turned off by specifying a bean of
type AuthenticationManager, AuthenticationProvider or UserDetailsService.
Closes gh-7958
Update management security to require an `ACTUATOR` role rather than
`ADMIN` by default. This should reduce the risk of users accidentally
exposing actuator endpoints because they happen to use a role named
`ADMIN`.
Fixes gh-7569
