Lint direct calls to `deref` or `deref_mut`

[clarfonthey]

Instead of calling x.deref() or x.deref_mut(), &*x and &mut *x should be recommended instead.

[ishitatsuyuki]

+1. This should tagged as easy (and attract some bored people from TWiR).

[oli-obk]

Probably should not lint if it's part of a method chain

[tommilligan]

I'd like to take this if still valid

[ThibsG]

Can we consider this one done?
Seems that trigger failed on 'Closes' in the PR

[oli-obk]

The PR was closed due to inactivity, so this hasn't been merged yet.