Inconsistent feature naming

[joshtriplett]

What it does

We could lint (at a warn-by-default level) if the set of non-deprecated features are not consistently named, such that some use _ and some use -.

This should wait until we have deprecated lints, and deprecated lints should be ignored for the consistency check, so that people can have compatibility features.

Advantage

This would encourage consistency in naming.

Drawbacks

It's a style matter, so it's likely to be divisive. Some people will appreciate lints on style matters, and others may find them annoying.

Example

[features]
my_feature = ["dep:a"]
my-other-feature = ["dep:b"]

Could be written as:

[features]
my-feature = ["dep:a"]
my-other-feature = ["dep:b"]

[epage]

Blocked on #7130.

We have restricted lints for forcing a specific naming style. This has the advantage of being able to be warn by default. This can lead to breaking changes, hence the deprecated condition.