Add option to retrieve all instrumented methods

[Henning-Schulz]

It may happen that some configured instrumentation silently has no effect. Currently, it is very hard to find the root cause. To narrow down the problem, it would be very helpful to have an option to see all currently instrumented methods and the rules that are applied to them. One option is a button in the configuration UI that retrieves and shows such a (potentially filtered) list, e.g.,

my.package.ClassA.methodA:
  - r_trace_method
  - r_method_metric
my.package.ClassB.methodB:
  - r_trace_method
  - r_my_custom_rule
...