Pass all instrumented metadata into splitComponentLoaders

[micburks]

With fusionjs/fusion-cli#769

Pass __I18N_KEYS from instrumented promise into splitComponentLoaders. The only consumer of splitComponentLoaders right now is fusion-plugin-i18n, but if the need arises in the future this is simpler to expand upon if all metadata is passed in together.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0b78ae4). Click here to learn what that means.
The diff coverage is 50%.

@@            Coverage Diff            @@
##             master     #249   +/-   ##
=========================================
  Coverage          ?   78.96%           
=========================================
  Files             ?       13           
  Lines             ?      271           
  Branches          ?       58           
=========================================
  Hits              ?      214           
  Misses            ?       40           
  Partials          ?       17

Impacted Files	Coverage Δ
src/async/split.js	58.69% <50%> (ø)

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0b78ae4). Click here to learn what that means.
The diff coverage is 50%.

@@            Coverage Diff            @@
##             master     #249   +/-   ##
=========================================
  Coverage          ?   78.96%           
=========================================
  Files             ?       13           
  Lines             ?      271           
  Branches          ?       58           
=========================================
  Hits              ?      214           
  Misses            ?       40           
  Partials          ?       17

Impacted Files	Coverage Δ
src/async/split.js	58.69% <50%> (ø)

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@0b78ae4). Click here to learn what that means.
The diff coverage is 50%.

@@            Coverage Diff            @@
##             master     #249   +/-   ##
=========================================
  Coverage          ?   78.96%           
=========================================
  Files             ?       13           
  Lines             ?      271           
  Branches          ?       58           
=========================================
  Hits              ?      214           
  Misses            ?       40           
  Partials          ?       17

Impacted Files	Coverage Δ
src/async/split.js	58.69% <50%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[rtsao]

This is a breaking change, right?

A bit hacky, but I wonder if a breaking change could be avoided by adding extra properties to the chunkIds array.

I think the hackiness is acceptable considering:

1. It's not really part of our public API, we just use this in our own plugins
2. Suspense will eliminate the need for all of this stuff anyways

[micburks]

Yes it's breaking technically, and yes we only use it in the i18n plugin. I really only made it breaking to come up with a more extensible API, but that is assuming splitComponentLoaders stays around when Suspense comes or if webpack was replaced. It can be avoided if we just pass the keys in as a second parameter, unless you consider a function signature change to be breaking because of flow.

Extra properties on the array is a bit goofy, but at the same time this is a pretty insignificant (and probably temporary) feature so I'm okay if that's the decision.