Migrate to redux@4

[tim-lai]

Content & configuration

all config, plugin, etc.

Is your feature request related to a problem?

Redux@4 breaking change: Forbid subscribe() and getState() while reducer is running. Ref here

PR #6330 is related, and #6331 are reverted the dependency change back to redux@3.

Swagger Editor unit tests fail with following error message:

Error: You may not call store.getState() while the reducer is executing. The reducer has already received the state as an argument. Pass it down from the top reducer instead of reading it from the store.

Swagger UI tests do not currently capture breaking changes from redux@4.

This change will require refactor changes to multiple reducer files.

Describe the solution you'd like

Describe alternatives you've considered

Additional context

[tim-lai]

closing as obsolete. SwaggerUI@4 implements React@17 and Redux@4