Remove #[non_exhaustive] on enum Ime

[dhardy]

• Tested on all platforms changed
• Added an entry to the changelog module if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality

This is a partial revert of #4647.

Enum Ime should not be #[non_exhaustive] since ignoring variants could lead to a mis-match between in-application and external representation of text contents and thus bad behaviour.

[ogoffart]

I think it is sad that you need to use nightly rust to get decent warning about non_exhaustive missing variable (non_exhaustive_omitted_patterns)

[dhardy]

@ogoffart you can read my thoughts on that here. Even if it were stable, it wouldn't change my position on the changeset in this PR.

[kchibisov]

Enum Ime should not be #[non_exhaustive] since ignoring variants could lead to a mis-match between in-application and external representation of text contents and thus bad behaviour.

While this is true, doing so would mean a breaking change for winit, since it's a semantic change that requires a semver bump, and we can still add those if we e.g. make those events opt-in, so non exhaustive doesn't really change much here.