Change event to event_key where it refers to an EventKey

[SteveAlexander]

Objective

The ECS code to do with Observers was recently refactored to use an EventKey newtype. On reading through the PR, I was a bit confused that sometimes a variable called event refers to an Event and sometimes it refers to an EventKey. I think the code is clearer when event refers to an Event and event_key refers to an EventKey.

Solution

This PR renames some uses of event to event_key.

Testing

• Did you test these changes? If so, how?

I ran cargo run -p ci -- tests

• Are there any parts that need more testing?

No

• How can other people (reviewers) test your changes? Is there anything specific they need to know?

No.

• If relevant, what platforms did you test these changes on, and are there any important ones you can't test?

Probably not relevant, but MacOS.

[github-actions]

Welcome, new contributor!

Please make sure you've read our contributing guide and we look forward to reviewing your pull request shortly ✨

[SteveAlexander]

And now I remember that backtick has a special meaning in zsh, and my commit message doesn't make sense. 🤦‍♂️

[copygirl]

And now I remember that backtick has a special meaning in zsh, and my commit message doesn't make sense. 🤦‍♂️

You can still change your commit message and force-push to your PR branch.

[SteveAlexander]

@copygirl thanks!

[SteveAlexander]

Thanks for the reviews @Zeophlite and @mockersf