#9307 Python: avoid assigning same port number to multiple grpc sessions

* Python: avoid assigning same port number to multiple grpc sessions
* Add retry count when checking for port number file
* Use grpc to find and use port number
* Add test used to start several instances of resinsight at the same time
Testing up to 50 instances works well

* Python: allow launch_port == 0 to assign port by GRPC in Instance.launch().
Also allow longer wait before failing the port number file reading:
it can take some time to launch when launching lots of instances at
the same time.

ApplicationLibCode/Application/Tools/RiaArgumentParser.cpp

@@ -76,6 +76,11 @@ bool RiaArgumentParser::parseArguments( cvf::ProgramOptions* progOpt )
                              "[<portnumber>]",
                              "Launch as a GRPC server. Default port is 50051",
                              cvf::ProgramOptions::SINGLE_VALUE );
+    progOpt->registerOption( "portnumberfile",
+                             "[<filename>]",
+                             "Write the port number to this file.",
+                             cvf::ProgramOptions::SINGLE_VALUE );
+
     progOpt->registerOption( "startdir", "<folder>", "Set startup directory.\n", cvf::ProgramOptions::SINGLE_VALUE );
 
     progOpt->registerOption( "summaryplot",