[Feature Request]: add an option to show summary of lints

[dclong]

Description

When a relatively medium/large project migrates to clippy, there might be a large number of lint warnings. It helps if there's an option to show counts of lints. For example,

LINT_1: n1
LINT_2: n2
...

And best if the above summary is sorted according to counts.

[ericwu17]

I think this would be a great idea and it would certainly be helpful in situations where clippy returns a long list of results!

@rustbot claim

[dclong]

Not all lint warnings are automatically fixable by Clippy. So, it's even better if the summary also contains info about how many warnings in each lint is automatically fixable.

[ericwu17]

I think this issue should actually be moved to the cargo repository, since this is a feature that requires changes to the behavior of cargo clippy. I've created a new issue in the cargo repository for now.