Move crypto migration

[yostyle]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Move crypto rust migration in the right place.

Motivation and context

Keys migration from kotlin to rust crypto does not work when an account has a single session and no backup.
@BillCarsonFr is aware about this problem

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[yostyle]

Signed-off-by: yostyle y.pintas@gmail.com

[BillCarsonFr]

LGTM

[yostyle]

Thanks @bmarty @BillCarsonFr