Add `resetCaches()` method to Caffeine/ConcurrentMapCacheManager

As an alternative to the proposal in PR #35821, we're adding a `resetCaches()` method to `CaffeineCacheManager` as well as `ConcurrentMapCacheManager`, both of which have a dynamic versus static mode which suggests a specific reaction on reset: either removing all dynamically registered cache instances, or simply clearing the cache entries in the fixed static cache regions.