Add opportunistic hauling to Grower loading process

[KongMD-Steam]

What would you like to see added to the mod? When loading a Pawn Vat or Organ Vat, pawns will not grab nearby stacks of the same ThingDef when they still have carrying capacity (a.k.a. opportunistic hauling). Implement this.

Example illustrating this enhancement: a) Start growing a new human clone b) Pawn takes job and grabs a 25x stack of Nutrient Solution c) With this enhancement, the pawn will also grab the 25x stack in the adjacent tile, because he has a carry capacity of 75. Without it, the pawn will go to the pawn vat holding only 25x nutrient solution.

[KongMD-Steam]

Complete. Relevant commits below. Pawn Vat: 4d8e2cb0256cbf4d48523956f167422833df1d81 Organ Vat: 126f5179a79e1fd7a8d8333aab95b498de7d3831