feat: Introduce a library for embedded iframe <-> host communication

[suddjian]

SUMMARY

This library is pretty simple, the code comments should explain everything.

This also uses the new library to provide a method to the sdk.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[suddjian]

I didn't realize this before but & actually starts a process in the background instead of working like Promise.all

[ad-m]

Suggested change

	"build": "tsc ; babel src --out-dir lib --extensions '.ts,.tsx' ; webpack --mode production",
	"build": "tsc && babel src --out-dir lib --extensions '.ts,.tsx' && webpack --mode production",

I suggest use && to execute that in series only if the predecessor was successful. In other words, stop as soon as an error occurs.

[suddjian]

These aren't really dependent on each other's result. Running each of them regardless of the others' status can output more useful information in the case of an error. Ideally I'd like to run them in parallel and wait for all to complete before the command exits, but I am not familiar with a convenient way to do that without writing a script, and that seems like overkill since these all run in about a second.

[lilykuang]

LGTM. please fix lint before merge :)

[codecov]

Codecov Report

Merging #18652 (b48e636) into master (85c8d01) will decrease coverage by 0.08%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master   #18652      +/-   ##
==========================================
- Coverage   66.30%   66.22%   -0.09%     
==========================================
  Files        1595     1605      +10     
  Lines       62629    62797     +168     
  Branches     6308     6341      +33     
==========================================
+ Hits        41527    41585      +58     
- Misses      19453    19560     +107     
- Partials     1649     1652       +3     

Flag	Coverage Δ
javascript	51.28% <80.00%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset-frontend/src/embedded/index.tsx	0.00% <0.00%> (ø)
...ackages/superset-ui-switchboard/src/switchboard.ts	100.00% <100.00%> (ø)
.../src/explore/components/DataTableControl/index.tsx	74.28% <0.00%> (-23.09%)	⬇️
...et-frontend/src/explore/reducers/exploreReducer.js	25.71% <0.00%> (-7.62%)	⬇️
...re/components/controls/DatasourceControl/index.jsx	72.36% <0.00%> (-5.90%)	⬇️
.../src/dashboard/components/BuilderComponentPane.tsx	78.94% <0.00%> (-4.39%)	⬇️
...tiveFilters/FiltersConfigModal/FilterTitlePane.tsx	81.25% <0.00%> (-3.75%)	⬇️
...onfigModal/FiltersConfigForm/FiltersConfigForm.tsx	59.01% <0.00%> (-0.86%)	⬇️
...eFilters/FiltersConfigModal/FiltersConfigModal.tsx	79.39% <0.00%> (-0.24%)	⬇️
.../explore/components/ExploreViewContainer/index.jsx	56.98% <0.00%> (-0.16%)	⬇️
... and 80 more

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