Maintenance development to fix all GitHub Actions (lint, unitTest) errors

[mrtamm]

It contains more than hundred changed files but, in general, they can be grouped:

1. Deprecated APIs:
   • ioutils: use corresponding methods in os or io packages
   • github.com/golang/protobuf/jsonpb -> google.golang.org/protobuf/encoding/protojson
   • github.com/golang/protobuf/proto -> google.golang.org/protobuf/proto
   • google.golang.org/grpc -> google.golang.org/grpc/status
   • due to API changes, had to regenerate ProtoBuf code using protoc
   • due to upgraded Protobuf CLI tools, had to update Makefile
2. error checking: added more error checks where it was properly done
3. Due to more specific error checking, unit tests discovered more problems, due to which those tests had to be fixed as well.
4. Had to upgrade github.com/shirou/gopsutil -> github.com/shirou/gopsutil/v3 as it did not work well on MacOS
5. Other minor specific deprecated functionality: had to replace with other types/methods
6. Updated GitHub Actions (tests.yml) to optimise the workflow (removed fixed go versions by referring to go.mod; improved workflow caching thanks to actions/setup-go@v5 which does it by default)
7. Update direct go dependencies.