Reimplement Alert matching native compose

[dfabulich]

Fixes #135

This is a pretty extensive PR. As @joshuakcockrell pointed out, Skip alerts didn't look very much like a "stock" Compose alert. Compose offers two APIs for alerts, a high-level AlertDialog which gives you an opinionated container with an expected look and feel, and a low-level BasicAlertDialog where you do everything yourself.

Skip's implementation used BasicAlertDialog, but it didn't adhere to the Material Design that AlertDialog provided; as a result, it felt very iOS-y and not very native to the platform.

Ideally, we'd just pass everything we need to AlertDialog, but we can't do that, because AlertDialog supports only two buttons (confirm + dismiss), and doesn't support embedding text fields.

Soooo I forked AlertDialog from the original Compose sources, and checked it in as SkipAlertDialog.kt with some minor changes. I then added native AlertDialog playgrounds to the showcase, and verified that SkipAlertDialog's implementation was a pixel-perfect match for AlertDialog.

With that done, I added support for any number of neutral buttons to AlertDialog, added support for text fields, and added a scrolling container, allowing users to scroll to read very long messages.

I took screenshots of each of the dialogs comparing them to the standard. The only difference now is that SkipAlertDialog puts the destructive button above the cancel button in the long button titles case, but that feels right to me, so I left that difference in.

Skip Pull Request Checklist:

• REQUIRED: I have signed the Contributor Agreement
• REQUIRED: I have tested my change locally with swift test
• OPTIONAL: I have tested my change on an iOS simulator or device
• OPTIONAL: I have tested my change on an Android emulator or device
• REQUIRED: I have checked whether this change requires a corresponding update in the Skip Fuse UI repository (link related PR if applicable)
• OPTIONAL: I have added an example of any UI changes in the Showcase sample app

skiptools/skipapp-showcase#63

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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes.

I used Cursor to copy the code from Compose. I carefully reviewed every line, and manually tested thoroughly in the showcase.

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[marcprux]

Intriguing! Could you post some of the screenshots?

[joshuakcockrell]

Oh boy I'm excited to see this.

[dfabulich]

New playground

Title only

Title + message

Long message

… but, in Skip, now you can scroll it!

Long button titles

It feels right to me to put "destructive" on the bottom.

Two buttons

Three buttons and five buttons (Skip only)

Text fields (Skip only)

[marcprux]

Looks great! Thanks!