List starting materials first in Synthesis information item select

[jdbocarsly]

Often, when searching for a starting material to add to synthesis information, other items that have used/mentioned that starting material come up before the actual starting material. It would be nice if we could somehow weight the starting materials to come up first in the list (but only for Synthesis Information. For other Item Selects, it may make sense for Samples or Cells to come first)

[ml-evs]

This kind of works against the new searching approach based on word boundaries which is only a binary yes/no match with no sorting, but you could also try using the old methods (exposed by prepending "%" to your search in those boxes) which uses the old FTS index that is weighted. We could also consider removing description search from the pure regex which is maybe less useful