Allow use of "/" in rule names

[krypt-lx]

Currently it is impossible to use "/" in name of os some rules (at least of swift_library).
It makes some third party rulesets incompatible, for example with_cfg:
https://github.com/fmeum/with_cfg.bzl

related issues in different repos:
bazelbuild/rules_apple#2546
fmeum/with_cfg.bzl#122