fix(android): Improper serialization of image uri in save instance state

[breautek]

Platforms affected

Android

Motivation and Context

The imageUri field is not properly restored if the activity is killed,
which can cause further issues.

This is because imageFilePath was used instead for the imageUri which only contains the
path of the original URI, losing the scheme in the process.

Description

Serialize using imageUri.toString() instead of using the imageFilePath

Testing

paramedic testing + testing with Don't Keep Activities developer option enabled.

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[breautek]

For clarity... The difference is imageUri will start off with a Uri object representing content://some-path/... or file:///some-path/... but if the activity was destroyed, it will get restored with an Uri representing /some-path/, missing the Uri scheme.