chore: expose DET utils for flutter plugin

[Mercy811]

Summary

https://amplitude.atlassian.net/browse/AMP-96756

Expose default event tracking utils so that they can be used in the Flutter iOS plugin.

• Create a class DefaultEventUtils
• Call DefaultEventUtils. trackAppUpdatedInstalledEvent() to track app updated & installed events

Checklist

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[github-actions[bot]]

:tada: This PR is included in version 1.4.4 :tada:

The release is available on:

• GitHub release
• v1.4.4

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