Refactor permisions can_read_route?

[Gerg]

• Use role_applies? with the existing roles constant, rather than querying the user's org and space membership
• Remove duplicate tests

Thanks for contributing to cloud_controller_ng. To speed up the process of reviewing your pull request please provide us with:

• A short explanation of the proposed change:

• An explanation of the use cases your change solves

• Links to any other associated PRs

• [x] I have reviewed the contributing guide

• [x] I have viewed, signed, and submitted the Contributor License Agreement

• [x] I have made this pull request to the main branch

• [x] I have run all the unit tests using bundle exec rake

• [ ] I have run CF Acceptance Tests