Update go package names to hyperledger/fabric-protos-go-apiv2

I believe `https://github.com/hyperledger/fabric-protos-go` is deprecated, and `https://github.com/hyperledger/fabric-protos-go-apiv2` is the latest fabric-protos-go package.
Hence this needs to be updated in all `.proto` definitions as:
```
option go_package = "github.com/hyperledger/fabric-protos-go-apiv2";
```

This is so that if some other's project's `.proto` depends upon fabric-protos, then on compiling it created dependency to deprecated version i.e. `github.com/hyperledger/fabric-protos-go`, which then later on create conflicts with go applications depending on this proto and fabric-protos.
I'm a maintainer/co-owner of Hyperledger/Cacti, where we are facing this issue.

I've a bash script to do this (which is what I'm using for workaround), if you are okay with it, I can create PR for this.

script:

Script

#!/bin/bash


ROOT_DIR=${1:-'..'}

pushd $ROOT_DIR

files=$(find ./fabric-protos -name *.proto)

for filename in $files

do

  sed -i'.scriptbak' -e ' s#^option go_package = "github.com/hyperledger/fabric-protos-go/#option go_package = "github.com/hyperledger/fabric-protos-go-apiv2/#' "$filename"

  rm -rf $filename.scriptbak

  cat $filename | grep "option go_package"

done

popd $ROOT_DIR