Remove use of ClassKey

[pjfanning]

• relates to consider modifying ClassKey to not keep a ref to the class instance jackson-databind#3774
• looks like 3774 will not be done for 2.15 release and it turns out that using Class references as Map keys is a bad idea
• this will mean breaking some little used APIs. I will document what users of these APIs will need to do when they upgrade.

In v2.14.3, these little used APIs (recently added and still changing):

• ScalaAnnotationIntrospectorModule.setDescriptorCache
• ScalaAnnotationIntrospectorModule.setScalaTypeCache

In v2.15.0, these APIs will remain deprecated but the input types will change:

• ScalaAnnotationIntrospectorModule.setDescriptorCache - input and return type changes to LookupCache[String, BeanDescriptor]) - was LookupCache[ClassKey, BeanDescriptor])
• ScalaAnnotationIntrospectorModule.setScalaTypeCache - input and return type changes to LookupCache[String, Boolean]) - was LookupCache[ClassKey, Boolean])

New functions added in v2.14.3 to replace these APIs:

• ScalaAnnotationIntrospectorModule.setDescriptorCacheSize(size: Int) - beware that this clears existing entries in the descriptor cache
• ScalaAnnotationIntrospectorModule.setScalaTypeCacheSize(size: Int) - beware that this clears existing entries in the scala type cache
• setLookupCacheFactory(lookupCacheFactory: LookupCacheFactory) - beware that this clears existing entries in both caches

LookupCacheFactory is a new trait:

trait LookupCacheFactory {
  def createLookupCache[K, V](initialEntries: Int, maxEntries: Int): LookupCache[K, V]
}

Example implementation:

  class ConcurrentLookupCache[K, V]() extends LookupCache[K, V] {
    final private val cache = TrieMap.empty[K, V]

    override def put(key: K, value: V): V =
      cache.put(key, value).getOrElse(None.orNull).asInstanceOf[V]

    override def putIfAbsent(key: K, value: V): V =
      cache.putIfAbsent(key, value).getOrElse(None.orNull).asInstanceOf[V]

    override def get(key: Any): V = {
      cache.get(key.asInstanceOf[K]).getOrElse(None.orNull).asInstanceOf[V]
    }

    override def clear(): Unit = {
      cache.clear()
    }

    override def size: Int = cache.size
  }

  object ConcurrentLookupCacheFactory extends LookupCacheFactory {
    override def createLookupCache[K, V](initialEntries: Int, maxEntries: Int): LookupCache[K, V] =
      new ConcurrentLookupCache[K, V]
  }