build: add plugins framework to learner dash

[jsnwesson]

This PR adds the frontend plugin framework in Learner Home.

This PR also includes:

• Add a PluginSlot to the Side Navigation Bar widget, both for LoadedSideBar and NoSideBar
• Add mock config object to PluginSlot.js to explicitly pass URL of Profile Plugin
• Remove the Optimizely experiments until we decide to bring any in (ie. Recommendations) for the POC

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (82ff0d7) 96.46% compared to head (bdbe684) 96.08%.

Additional details and impacted files

@@                      Coverage Diff                      @@
##           aperture/PluggableDashPOC     #215      +/-   ##
=============================================================
- Coverage                      96.46%   96.08%   -0.39%     
=============================================================
  Files                            195      195              
  Lines                           1839     1839              
  Branches                         322      322              
=============================================================
- Hits                            1774     1767       -7     
- Misses                            60       67       +7     
  Partials                           5        5              

Files	Coverage Δ
...shboardHeader/CollapsedHeader/CollapseMenuBody.jsx	88.88% <ø> (ø)
...rs/LearnerDashboardHeader/ExpandedHeader/index.jsx	100.00% <ø> (ø)
...ontainers/WidgetContainers/LoadedSidebar/index.jsx	100.00% <ø> (ø)
...ainers/WidgetContainers/NoCoursesSidebar/index.jsx	100.00% <ø> (ø)

... and 3 files with indirect coverage changes

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[MaxFrank13]

LGTM!

One thing I noticed about the Optmizely variation error that we were seeing is that it can also be fixed by providing a default value when createContext is called here.

That ended up looking like this:

export const PaintedDoorExperimentContext = React.createContext({
  experimentVariation: '',
  isPaintedDoorNavbarBtnVariation: false,
  isPaintedDoorWidgetBtnVariation: false,
  isPaintedDoorControlVariation: false,
  experimentLoading: true,
});

I don't think this is blocking seeing as we are just trying to get the POC together but thought it was valuable... context 😉

[jsnwesson]

@MaxFrank13 frustratingly, the configuration you're suggesting already exists here, but the error message appears the same when they're toggled to true.