We load the entire bundle only to use the objectInspector reducer in devtools/client/inspector/reducers.js#24-28.
We should try to only load the reducer file instead.

This patch exposes the objectInspector reducer as a regular
file that can be required in the devtools codebase.
This should make things faster to start as we won't need
to load the entire bundle (especially for the inspector where
the reps is only used when navigating to specific subpanels).
This means we need to remove the flow typing for now since
we don't have a cross-toolbox build process like we have
in the debugger.

Depends on D47728

If you want a simpler inspector-only fix which allows you to keep flow typing, the following patch worked fine for the inspector metrics tests: https://hg.mozilla.org/try/rev/53f3108af87869c2588843693f439d1af55d6eb3

Backed out 2 changesets (Bug 1584973) for devtools node failure.

Backout: https://hg.mozilla.org/integration/autoland/rev/bafc4821f21d9a6278440163c0f0f2a5b14ce747

Push that started the failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception&revision=c06273b257694bd36d2ecff45d351c9bdd638b4a&selectedJob=269309344

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=269309344&repo=autoland&lineNumber=371

There are also some mochitest devtools failures:
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=269327286&repo=autoland&lineNumber=2625

Fixed failures: https://treeherder.mozilla.org/#/jobs?repo=try&revision=a860164c426240667b80b4c89a132468318f03cd

https://hg.mozilla.org/mozilla-central/rev/3bb37c5f2ba8
https://hg.mozilla.org/mozilla-central/rev/df5e4d89de17