plasma go mod migration

For S3 plugin, plasma has a direct dependency on tools-common package and aws-sdk-go. Both the packages are not present in elixir manifest. The aws-sdk-go seemed to be removed from the neo manifest as backup had moved to go. mod. In addition, tools-common has its own dependencies. When I tried to build, I had to  add ~ 10+ packages to my local manifest file. Hence I think it is better for plasma to migrate to go.mod. Besides, from MB-53361 (indexing),  going forward build team seems to move towards go module as a way of dependency management for elixir releases rather than using go-deps (old and deprecated). Hence filing the MB.