bitbake: bitbake-diffsigs: fix regression after recent server changes

We were bridging the gap between the server and UI here by calling a
bb.siggen.find_siginfo, a function defined and set on that module from
the metadata. This worked from the UI side before but since the recent
server changes is no longer accessible. Create a new command so this can
execute on the server side and return the result by way of a new event.

(We're still running compare_sigfiles() on the signature generator but
that isn't quite the same thing and does still work.)

Fixes [YOCTO #11844].

(Bitbake rev: fdcea991baa4f83d9c98d468d7b49c8c388a4a15)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -819,3 +819,11 @@ class NetworkTestFailed(Event):
     """
     Event to indicate network test has failed
     """
+
+class FindSigInfoResult(Event):
+    """
+    Event to return results from findSigInfo command
+    """
+    def __init__(self, result):
+        Event.__init__(self)
+        self.result = result