Ember 6 Compat: Remove "action", Change to Class Style

[ladadeedee]

Ember 6 removes support for "action" helper in templates officially, after a long period of deprecation. https://deprecations.emberjs.com/id/template-action/

This PR does two big things and a few minor things:

1. Replace all uses of action in templates with either direct references or fn helper if currying is needed
2. Updates JS files to be in class syntax rather than classic syntax
3. Remove custom handleMouseEnter code on select-dropdown-option, simplifying code
4. Removes oninput binding on the input element since there was an issue with the order of events fired. Its functionality was moved into the existing keypress handler. This required a minor workaround since the input element's value is not updated until after the key has been handled, requiring us to concat the current value plus the newly-entered key
5. Remove old IE bug handling in blur()
6. Renames dropdown handler due to a conflict between the passed-in value (a string, to specify custom dropdown component) and a function
7. Likewise, removes select from being passed to the dropdown component due to naming conflicts. Use parent.select instead

Basic, functionality appears to be working. I'm opening this as a draft to gather feedback.

[aluink]

Should this be this.list now?

[ladadeedee]

We can change a lot of these this.get() calls but I don't want to cause too much change in this PR. this.set() is most likely off-limits until we move to Glimmer.

[btecu]

Excellent work @ladadeedee!

Would it be possible to separate some of the smaller changes into different pull requests?

The one concern I have is about oninput -> keypress conversion.

[ladadeedee]

Once you finish your cleanup, I'll rebase (painfully) and see where we stand.

[ladadeedee]

We've manually applied pretty much all of the changes here.