Bazel: Clean up package visibility settings

For packages having a default visiblity defined, it is redundant to also
set the same visibility per package, so remove those.

For packages that only have one rule, and its visibility differs from the
default visibility, remove the default visibility.

Also clean up wrapping of some of the default definitions.

Change-Id: I9e81c3f724b4ffde7a652b485d33c650866ad122