Use sendMultipartTextMessage for respond with sms

Long messages won't send properly if used in the respond-with-sms API.
Use sendMultipartTextMessage to get around this. Also display an error
toast if the message didn't send properly.

Bug: 65087120
Test: manual
Change-Id: I31ba24a0600e42010752b1216b1aca7d1098b319
3 files changed