feat: Update Appwrite package to v8.1.0 to add support for Appwrite v1

[ghost]

What does this PR do?

Add support for Appwrite v1 (Dart package version: v8.1.0 (latest))

Test Plan

Updated the code to make it work with the new dependency changes.

Tried out on Android 10

Related PRs and Issues

Closes appwrite/appwrite#4259

Have you read the Contributing Guidelines on issues

Yes

[gewenyu99]

The changes themselves look good, I'm gonna try to run this quickly to see if it's working 💯

[gewenyu99]

@VoidCupboard It'll be great to see some screen caps on devices, so I can be sure they're working fine as well.

Great job 💯

[ghost]

Thanks a bunch, @gewenyu99 :)

Here is the video showing the demo on a Physical Device (Android 10):

appwrite_quiz_demo.mp4

[gewenyu99]

These changes look good now!

[christyjacob4]

THANK YOU! All changes merged 🥳

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