Auto-configured JCacheMetrics cannot be customized

[wilkinsona]

See #46017 for background.

Micrometer is going to provide a setting that allows the JCache removals to be registered as a function counter. As far as I can tell, that option won't be usable in Boot as the auto-configured JCacheCacheMeterBinderProvider isn't @ConditionalOnMissingBean so there's no easy way to define your own provider with a custom JCacheMetrics that uses a function counter for removals.

A couple of options:

1. Make the auto-configured JCacheCacheMeterBinderProvider @ConditionalOnMissingBean
2. Provide a configuration property, something like management.metrics.jcache.register-removals-as-function-counter, to control Micrometer's new setting.

We could do either or both of these.