* Support negative-valued action parameters
by converting them in the Python helper code into a positive value
whose bit pattern is the 2's complement representation of the negative
value.
* Update versions of protobuf and grpc installed, install p4testgen
Update protobuf from v3.6.1 to v3.18.1
Update grpc from v1.17.2 to v1.43.2
Both of those versions have been long tested in the p4-guide repo
install scripts.
Update BMv2, PI, p4c, and ptf to latest versions as of 2023-Jun-24
Enable compilation of p4testgen
* Change method to install ptf
I found that the former way that I am replacing did not seem to install
it correctly.
* Make clean.sh remove sources for protobuf and grpc
Saves disk space for the image. protobuf and grpc source code is easily
obtainable from public sources if the user wishes.
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