Update VPE dependencies and rebuild interface

[arthurkehrwald]

I installed the latest versions of grpcio, grpciotools and protobuf, regenerated the platform interface scripts using mpf/platforms/visual_pinball_engine/generate.py and tested it with VPE.

Fixes #1864

[arthurkehrwald]

I've added a new RPC to the service definition. It is a simple ping function that I will use in the VPE integration to check if MPF is ready. Previously, VPE simply waited for 1,5 seconds and assumed it was ready, but this can fail on slow computers and wastes time on fast ones. GRPC provides ways to wait for the connection to be ready that would be preferrable, but they are not supported on grpc-dotnet with .netstandard2.1.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[arthurkehrwald]

I've added the MPF version to the ping response so VPE can accommodate different versions of MPF in the future.