Hold metadata caches which maps various JVM constants into pre-parsed forms.
For example, bean property accessors, or normalized enum constants.
Note that unlike most JdbiConfig types, this cache is Jdbi level and shared,
so it should not hold data that needs to respect reconfiguration.
Additionally, currently there is no expiration policy, as nearly all keys are
references to JVM constant pool entries.
This makes it unsuitable as a general-purpose shared cache.