LSP diagnostic for recursive handler warning

[ceedubs]

Describe and demonstrate the bug

Recently @dolio added a warning for suspicious looking handlers that might result in quadratic behavior. The error message starts with:

  The recursive occurrences of the handler are called at a subset
  of the declared abilities, which might indicate that a separate
  handler is installed for each recursive call.
  
  To avoid performance problems, each handler should be installed
  only once.

It would be great if this resulted in LSP diagnostic warnings similarly to how unused local variables do.

Environment (please complete the following information):

• ucm --version 7f15363