[WIP] Refactor Meta's deps structure to an array of arrays.

[rwjblue]

/cc @krisselden @ef4

[rwjblue]

@krisselden - I updated this to use an array of arrays (instead of a map of arrays). I left it in two commits so that it was easy to compare the difference (in case you end up liking the map of arrays approach better).

The best summary of the new structure is from writeDep where we setup the structure:

    // add the subkey to the outerArray
    keyArray.push([
      subkey,
      // array of itemKeys for the subkey
      [
        [itemKey, value]
      ]
    ]);

[machty]

this used to be 5.4 http://numberofpeoplewhounderstandembermetal.com/

[chadhietala]

Nit: Can you do write${capitalized}, same goes for the other dynamic method. 😄

[rwjblue]

Updated #13660 to migrate to using the lodash-like object interface for this functionality. Closing this in favor of that.

@chadhietala - I'll make sure to incorporate your comments there though...

[homu]

☔ The latest upstream changes (presumably #13783) made this pull request unmergeable. Please resolve the merge conflicts.