Send sim change notification based on sim state change.

+ Send sim change notifications based on Sim state change rather then based
on subscription change.
+ Make SimSettings dynamically update based on subscriptions changed. Would
support hotswap which was not supported before this.

Bug: 20739298
Bug: 18385348
Change-Id: I5bb4b05f55b94eb0ed2a1a83fe2f168192b2b684