devel/go-tools: Update to 0.1.7

- assign MAINTAINER
- switch to USES=go:modules
- bump PORTEPOCH due to new versioning scheme
- take over maintainership of this unmaintained port
- adjust list of shipped commands to current set
- getgo/server is not shipped due to its awkward name
  and lack of usefulness to anybody outside of Google

PR:             259958