[🔥AUDIT🔥] [rg.audit.1] Add custom flow file for render-environment-jsdom to work around flowgen issue

[somewhatabstract]

🖍 This is an audit! 🖍

Summary:

• Add the faster flowgen script from Wonder Blocks, and include the "custom overrides" support.
• Fix some flow type issues for core and render-environment-jsdom.

Issue: FEI-4960

Test plan:

yarn clean && yarn build && yarn build:types && yarn build:flowtypes

Also check that the types will work for the usages I have to hand.

[changeset-bot]

🦋 Changeset detected

Latest commit: bdbff43

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@khanacademy/wonder-stuff-render-environment-jsdom	Patch
@khanacademy/wonder-stuff-core	Patch
@khanacademy/wonder-stuff-render-server	Patch
@khanacademy/wonder-stuff-sentry	Patch
@khanacademy/wonder-stuff-server	Patch
@khanacademy/wonder-stuff-testing	Patch

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[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/frontend-infra for changes to .changeset/eleven-trains-rush.md, build-scripts/gen-flow-types.ts, packages/wonder-stuff-core/src/types.js.flow, packages/wonder-stuff-render-environment-jsdom/src/types.js.flow

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[somewhatabstract]

Copied from Wonder Blocks, but edited to:

• Use the correct path for packages/wonder-stuff-*
• Remove React-specific tweaks