Only send pointer updates when useful.
Only send pointer updates when useful.

We also now actually update the internal representation of the pointer.

This was originally 5d80df18, but was accidentally reverted when
rebasing b4841e01f.

saketkumar95/zulip-android,prati0100/zulip-android,saketkumar95/zulip-android,abhaymaniyar/zulip-android,abhaymaniyar/zulip-android,prati0100/zulip-android,zulip/zulip-android,Sam1301/zulip-android,Sam1301/zulip-android,vishwesh3/zulip-android