This PR enables the [`no-action-modifiers`](https://github.com/ember-template-lint/ember-template-lint/blob/master/docs/rule/no-action-modifiers.md) template lint rule and removes all usages of the `{{action}}` modifier in core.
In general, instances of `{{action "x"}}` have been replaced with `{{on "click" (action "x")}}`.
In many cases, such as for `a` elements, we also need to prevent default event handling to avoid unwanted side effects. While the `{{action}}` modifier internally calls `event.preventDefault()`, we need to handle these cases more explicitly. For this purpose, this PR also adds the [ember-event-helpers](https://github.com/buschtoens/ember-event-helpers) dependency so we can use the `prevent-default` handler. For instance:
```
<a href {{on "click" (prevent-default (action "x"))}}>Do X</a>
```
Note that `action` has not in general been refactored away as a helper yet. In general, all event handlers should be methods on the corresponding component and referenced directly (e.g. `{{on "click" this.doSomething}}`). However, the `action` helper is used extensively throughout the codebase and often references methods in the `actions` hash on controllers or routes. Thus this refactor will also be extensive and probably deserves a separate PR.
Note: This work was done to complement #17767 by minimizing the potential impact of the `action` modifier override, which uses private API and arguably should be replaced with an AST transform.
Commits:
* Enable `no-action-modifiers` template lint rule
* Replace {{action "x"}} with {{on "click" (action "x")}}
* Remove unnecessary action helper usage
* Remove ctl+click tests for user-menu
These tests now break in Chrome when used with addEventListener. As per the comment, they can probably be safely removed.
* Prevent default event handlers to avoid unwanted side effects
Uses `event.preventDefault()` in event handlers to prevent default event handling. This had been done automatically by the `action` modifier, but is not always desirable or necessary.
* Restore UserCardContents#showUser action to avoid regression
By keeping the `showUser` action, we can avoid a breaking change for plugins that rely upon it, while not interfering with the `showUser` argument that's been passed.
* Revert EditCategoryTab#selectTab -> EditCategoryTab#select
Avoid potential breaking change in themes / plugins
* Restore GroupCardContents#showGroup action to avoid regression
By keeping the `showGroup` action, we can avoid a breaking change for plugins that rely upon it, while not interfering with the `showGroup` argument that's been passed.
* Restore SecondFactorAddTotp#showSecondFactorKey action to avoid regression
By keeping the `showSecondFactorKey` action, we can avoid a breaking change for plugins that rely upon it, while not interfering with the `showSecondFactorKey` property that's maintained on the controller.
* Refactor away from `actions` hash in ChooseMessage component
* Modernize EmojiPicker#onCategorySelection usage
* Modernize SearchResultEntry#logClick usage
* Modernize Discovery::Categories#showInserted usage
* Modernize Preferences::Account#resendConfirmationEmail usage
* Modernize MultiSelect::SelectedCategory#onSelectedNameClick usage
* Favor fn over action in SelectedChoice component
* Modernize WizardStep event handlers
* Favor fn over action usage in buttons
* Restore Login#forgotPassword action to avoid possible regression
