New lint suggestion `Error impl Error`

[JonathanWoollett-Light]

What it does

Warns on types which implement std::error::Error being named Error.

Advantage

Removes needing to document against using this common pattern.
The reasons against this pattern is that it can reduce readability and requires error types be renamed when imported (which can further reduce readability).

When you have 20 types named Error in your project it can become annoying.

Drawbacks

Adds an additional lint to clippy.

Example

#[derive(Debug, thiserror::Error)]
pub enum Error { /* ... */ }

Could be written as:

#[derive(Debug, thiserror::Error)]
pub enum MySpecificError { /* ... */ }

#[derive(Debug)]
pub enum Error { /* ... */}
impl std::error::Error for Error { /* ... */ }

Could be written as:

#[derive(Debug)]
pub enum MySpecificError { /* ... */}
impl std::error::Error for Error { /* ... */ }

[y21]

This is a pretty common pattern (even in the standard library there's io::Error and fmt::Error) so imo this should be a restriction lint if it gets added