Fixup line number for OpVectorShuffle ID error.

This CL updates the code to pull a valid instruction for the line number
when outputting a component error in OpVectorShuffle. The error line
isn't the best at this point as it points at the component, but it's
better then a -1 (turning to max<size_t>) that was being output.

The error messages has been updated to better reflect what the error is
attempting to say.

Issue 1719.