DiagnosticsHandler without reflection

Probe.sh sends commands to cluster nodes, and they are handled by each node's DiagnosticsHandler. "op" and "jmx" commands are handled via reflection.

However, reflection is not allowed by the GraalVM running in native mode, unless all attributes and methods of all protocols would be listed in a JSON file. This is apparently very costly as the native image builder creates a transitive closure over all classes whose methods and/or fields are listed in the JSON file, and thus includes too many classes in the native image.

Investigate creating a ProbeHandler for "jmx" and "op" commands, which does not use reflection. 2 alternatives come to mind:

• Offline creation and compilation: point to a list of protocols for which code is generated (an alternative ProbeHandler class). This class is then instantiated and set in the channel at runtime by the application
• Point to a running stack. The code uses reflection (obviously this needs to run in non-native mode) to generate the native ProbeHandler from the list of protocols running in the current stack. This code can then be compiled and used in native image generation.