[SMS Helper] Use simple=true parameter for fetching the list of all conversations

Summary

Use content://mms-sms/conversations?simple=true instead of just content://mms-sms/conversations which should work for more devices (and is reported to work on Samsung devices)

For some reason, this misses exactly one conversation on my phone and throws back one invalid thread ID -- I suspect this indicates that my message database is corrupt :shrug:

BUG: 401677

Test Plan

Before:

Lots of devices were not able to retrieve conversations. See bug 401677

After:

Hopefully all devices are able to retrieve conversations. At minimum, hopefully there are no regressions :)