Change MVT max integer to a lower more manageable number of 1 million

The maximum integer we were previously using as the upper boundary for our MVT cookie value seems to be *too high* for some JavaScript engines to compute and play nicely with. 

Our hypothesis is that using a smaller range of 0-1000000 should prevent incorrect calculations.

/cc @rich-nguyen @stephanfowler @wenjiaz @selwyn-mccracken