[image_picker] image picker memory leak fix on Android

[juliocbcotta]

Description

This PR tries to fix a memory leak in image picker plugin by unregistering the ActivityLifecycleCallbacks in the onDestroy of the view.

Related Issues

flutter/flutter#36520

Checklist

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• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See [Contributor Guide]).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the [Flutter Style Guide].
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy].
• I updated CHANGELOG.md to add a description of the change.
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Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

[cyanglaz]

LTGM!

[cyanglaz]

CI seems not happy about some java unit tests

[juliocbcotta]

@cyanglaz it is green.

[qwerqwq]

image_picker 有图片压缩的功能api吗

[cyanglaz]

@qwerqwq 目前还没有。如果您有兴趣可以开一个pr ：）