[FEAT]: Add intervention weights for relative importance in Optimize

[pascaleproulx]

This design allows users to provide a relative importance when optimizing multiple interventions at once.
Replace the current 'optimize' toggle with the new relative importance widget. Note that there will be no more ability to choose whether or not to optimize an intervention.

The dropdown has numbers between 1-10. The 'signal' visual is non-interactive and matches the selected number. The user may pick any number in each dropdown (e.g. for 3 interventions, the choice could be 1,3,3 or 5,5,5 (default) or 1,5,10). When the user clicks run, the weights should be converted into a fraction (i.e. compute the sum and transform each weight into a ratio of number/sum).