Add config hide placeholders type hints

[A4-Tacks]

In the inferred type hints, expand the line too long. add config to disable it.

Example

{"rust-analyzer.inlayHints.typeHints.hideInferredTypes": true}

use std::collections::HashMap;
fn foo(iter: Vec<Result<HashMap<String, String>, std::io::Error>>) {
    let output = iter.into_iter().collect::<Result<Vec<_>, _>>().unwrap();
}

Before this PR

let output: Vec<HashMap<String, String>> = iter.into_iter().collect::<Result<Vec<_ = HashMap<String, String>>, _ = Error>>().unwrap();

After this PR

let output: Vec<HashMap<String, String>> = iter.into_iter().collect::<Result<Vec<_>, _>>().unwrap();

[ChayimFriedman2]

I think I prefer the phrase to be positive, all other configs are this way. Also "placeholder" may not be clear to the user, so something like inferred_types = true by default.

[A4-Tacks]

I think I prefer the phrase to be positive, all other configs are this way.

There are already hideClosureInitialization, hideClosureParameter, and hideNamedConstructor, perhaps it would be better to maintain the same style with the hide prefix?

[ChayimFriedman2]

Thanks!