Implement foundation.e.mail.provider.AppContentProvider

Summary

AccountManager consumes an AppContentProvider but this one is not implemented in the new mail application

The problem

Steps to reproduce Open Settings > accounts > /e/ > Account sync

What is the current behavior?

Some extra switch button are displayed, when you click on it is worse. Several button switch are added with the on state.

What is the expected correct behavior?

No extra switch button.

Technical informations

Relevant logs (adb logcat)

03-22 12:18:32.271   490   490 I hwcomposer: [HWCDisplay] [Display_0 (type:1)] fps:21.659466,dur:1061.89,max:641.45,min:16.38  
03-22 12:18:32.332  3063  3755 E ActivityThread: Failed to find provider info for foundation.e.mail.provider.AppContentProvider
03-22 12:18:32.342  1005  1153 W SyncManager: failed sync operation JobId=108841 ***/e.foundation.webdav.eelo u0 [foundation.e.mail.provider.AppContentProvider] OTHER ExpectedIn=0s STANDBY-EXEMPTED(TOP) Reason=AutoSync, SyncResult: databaseError: true stats []
03-22 12:18:32.343  1005  1153 E SyncManager: not retrying sync operation because the error is a hard error: JobId=108841 ***/e.foundation.webdav.eelo u0 [foundation.e.mail.provider.AppContentProvider] OTHER ExpectedIn=0s STANDBY-EXEMPTED(TOP) Reason=AutoSync Retries=1

Relevant screenshots

cc @rhunault