Remove unused package dependencies and organize pubspec.yaml

[hjiangsu]

Pull Request Description

This PR removes some dependencies that are no longer being used. Additionally, it organizes the pubspec.yaml file so that packages are organized alphabetically (with the exception of custom/unpublished packages).

Note: this change will cause merge conflicts with any currently opened PRs that add/remove/change pubspec.yaml

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Side note: I hope to eventually reduce the number of external package dependencies that we currently have. There are a few reasons for this:

1. to cut down on overall package build sizes - the more external dependencies we rely on, the larger our final build
2. to reduce situations where we have to wait for a package to be updated (e.g., delays us from being able to upgrade to the latest Flutter version)

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Checklist

• If a new package was added, did you ensure it uses an appropriate license and is actively maintained?
• Did you use localized strings (and added appropriate descriptions) where applicable?
• Did you add semanticLabels where applicable for accessibility?