Lint against `HashMap`s where the key is not `Eq + Hash`

What it does

An empty HashMap<K, V> can be constructed with any type of key, but to actually allow inserting values into it, the key type must implement Eq and Hash.
This lint would warn if it encounters any type that does not implement Eq + Hash used as a HashMap key and, if possible, suggest deriving the missing traits (PartialEq, Eq, Hash).

Advantage

• The HashMap is fully usable.

Drawbacks

• There might be a legitimate use case for a HashMap without K: Eq + Hash (I don't know if there is one).

Example

use std::collections::HashMap;
struct Key(u32);
struct Other(HashMap<Key, String>);

Could be written as:

use std::collections::HashMap;
#[derive(PartialEq, Eq, Hash)]
struct Key(u32);
struct Other(HashMap<Key, String>);

Start from the issue's Rust example involving HashMap<Key, String> and determine how Clippy can identify key types lacking Eq and Hash. Review existing HashMap-related lint patterns and tests, then define completion as a warning for unusable key types with a valid derive suggestion where possible.