feat: storageRune.size method + sizeTree pattern

[harrysolovay]

A pattern for resolving a pallet-indexed lookup of storage-entry-size lookups.

import { sizeTree } from "capi/patterns/sizeTree.ts"
import { chain } from "polkadot_dev/mod.ts"

const result = await sizeTree(chain).run()

In this example result evaluates to something along the following lines:

{
  System: {
    Account: 1040,
    ExtrinsicCount: undefined,
    BlockWeight: 11,
    AllExtrinsicsLen: undefined,
    BlockHash: 32,
    ExtrinsicData: undefined,
    Number: undefined,
    ParentHash: 32,
    Digest: undefined,
    Events: undefined,
    EventCount: undefined,
    EventTopics: undefined,
    LastRuntimeUpgrade: 11,
    UpgradedToU32RefCount: 1,
    UpgradedToTripleRefCount: 1,
    ExecutionPhase: undefined
  },
  // other pallets...
}

Will hold off on merging until #655, so that we can ensure this pattern is accessible to NodeJS consumers.

@kianenigma, is this what you had in mind? As I understand it, we could take this a step further by iterating over the keys in storage maps... but that feels marginally wrong (in the same vein as Shawn's comment here).