Allow specifying EventStream

[eric-higgins-ai]

This PR contains a:

• [ ] bugfix
• [X] new feature
• [ ] code refactor
• [X] test update
• [ ] typo fix
• [ ] metadata update

Motivation / Use-Case

We have several bundles built using module federation and want to run dev servers for all of them in parallel. Currently this requires opening 1 event stream per bundle, which causes problems because Chrome limits open requests to a single domain to 6. This PR fixes that issue by exporting createEventStream and adding an eventStream to the middlware options, so we can create a single event stream and share it between all of our webpack instances.

[linux-foundation-easycla[bot]]

• :x: - login: @erichiggins0 / name: Eric Higgins . The commit (a9a0510d0874e272c52da975d28884ab2cf24d79) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[alexander-akait]

Please accapt CLA, thank you