Bind cache metrics from Spring's CacheManager

[jkschneider]

See spring-projects/spring-boot#11221 (comment)

[jkschneider]

The plan is to add an event listener somewhere in or around CacheManager to detect when a new cache has been added to the manager. From there, we can use Cache#getNativeCache() to retrieve the underlying cache and bind the correct MeterBinder.

[jkschneider]

We won't be able to accomplish this in Boot 1.5.x and prior.

[snicoll]

@jkschneider unfortunately, I think we have to let this one go. javax.cache.CacheManager has no event support for a cache being added which is a blocker on its own. I am not sure the other implementations are any easier in that area.

In the meantime, I've added auto-configuration support for caches with a service that allows you to bind the caches that are created programmatically. That doesn't work for caches created on the fly, which is quite annoying.

[jkschneider]

This was accomplished in spring-projects/spring-boot@0515ca0#diff-8af53ca5a010486793f937636f38863d