Convert "New menu" feature spec to a view spec

A feature spec to test this simple behavior takes about 2 minutes to run in CI. Everything it's testing is conditionals and href attributes, which can easily be done in a view spec that runs in about 8 seconds.

d1d8211c - Condense the "new_dropdown" layout partial

After converting the test that verifies this partial's behavior from a feature spec to a view spec, we're able to remove a few CSS classes that were only used for scoping tests found in the feature spec. All the view spec needs is the have_link matcher which allows us to check for a specific href attribute.

Baseline (feature spec)

Finished in 42.76 seconds (files took 7.44 seconds to load)
15 examples, 0 failures

After (view spec)

Finished in 10.81 seconds (files took 10.64 seconds to load)
10 examples, 0 failures

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54157