Prepare for 0.7.0

- update a few crates
- add a new version to the changelog
- update our crate versions

Prepare the changelog for 0.6.0. (linebender#1006)

Update fluent

Update examples to use reexported types

[mac] Fix crash when holding RefMut while showing context menu

Other events can arrive while we are showing the context menu. To work
around this, we need to not show the menu while holding a borrow on
the window state, and instead schedule it to be shown after we've
returned.

A consequence of this fix is that, currently, we don't actually use
the x, y values passed by the caller, and instead just always use
the last known mouse position.

Cargo.lock

ci: Do less work in CI

This reduces the amount of work we will do in CI in two ways:

- it moves the 'deny warnings' check to happen in the same
job as the `cargo test` check, because they both compile
at the same optimization level and we can reuse artifacts.

- it removes the 'cargo check' job, since any failure there
will also be caught in `cargo test`. If jobs were sequential
it might be worth checking first, to fail quickly, but
since jobs are parallel this is just extra work for no
tangible benefit.