[FEAT] Ask user where to create a new database

[PhilippC]

The current default is to create new databases in the "ExternalFilesDir" (https://learn.microsoft.com/en-us/dotnet/api/android.content.context.getexternalfilesdir?view=net-android-35.0) which is accessible for other apps (intentionally, such that sync apps can read/write it or create backups).

However, this behavior is not well explained/documented and not very intuitive to use (https://github.com/PhilippC/keepass2android/issues/2806).

When CreateDatabaseActivity opens, it should show a dialog asking where to place the file with these options:

• in ExternalFilesDir (not included in phone backup, accessible for other apps)
• in FilesDir (included in phone backup, not accessible for other apps)
• in NoBackupFilesDir (not included in phone backup, not accessible for other apps)
• location of the user's choice (including local files and cloud files)