Investigate if we can avoid repetitive build target visibility declarations

[oschaaf]

In our BUILD files, in envoy_cc_library, we have lots of repetition with respect to declaring visibility of targets. It would be nice if we could set this at the package level instead of declaring it in targets separately.

This came up in https://github.com/envoyproxy/nighthawk/pull/477/files/70502e1f2cea37b86edd180c54a66fea75843c17#r480474406

[1]

...
visibility = ["//visibility:public"],
...