Prior to this commit, MBeanExporter used
org.springframework.core.Constants which used reflection to find
constant fields in the MBeanExporter class. Consequently, one had to
register reflection hints in order to use MBeanExporter in a GraalVM
native image.
This commit addresses this by replacing the use of the `Constants`
class with a simple java.util.Map which maps constant names to constant
values for the autodetect constants defined in MBeanExporter.
See gh-30851
Closes gh-30846
679b668bbb