Update getting started docs
Update getting started docs

Add info on the restored iree-run-module
Make examples use a consistent file that exports its functions and add a note about exporting

Tested:
Ran all the commands to make sure they actually work.
PiperOrigin-RevId: 294763513

iree-org/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,google/iree