Tree: Compare cached flattened nodes with id key

[jacobroschen]

If a tree has a complex object for its nodes (deeply nested, etc), the keyboard select fails to work properly. This is due to the complex objects being compared by reference, instead of by value. To fix this, we are now finding the node by id, since that is a required value for every node.

---

CONTRIBUTOR checklist (do not remove)

Please complete for every pull request

• First-time contributors should sign the Contributor License Agreement. It's a fancy way of saying that you are giving away your contribution to this project. If you haven't before, wait a few minutes and a bot will comment on this pull request with instructions.
• npm run lint:fix has been run and linting passes.
• Mocha, Jest (Storyshots), and components/component-docs.json CI tests pass (npm test).
• Tests have been added for new props to prevent regressions in the future. See readme.
• Review the appropriate Storybook stories. Open http://localhost:9001/.
• The Accessibility panel of each Storybook story has 0 violations (aXe). Open http://localhost:9001/.
• Review tests are passing in the browser. Open http://localhost:8001/.
• Review markup conforms to SLDS by looking at DOM snapshot strings.

REVIEWER checklist (do not remove)

• TravisCI tests pass. This includes linting, Mocha, Jest, Storyshots, and components/component-docs.json tests.
• Tests have been added for new props to prevent regressions in the future. See readme.
• Review the appropriate Storybook stories. Open http://localhost:9001/.
• The Accessibility panel of each Storybook story has 0 violations (aXe). Open http://localhost:9001/.
• Review tests are passing in the browser. Open http://localhost:8001/.
• Review markup conforms to SLDS by looking at DOM snapshot strings.

Required only if there are markup / UX changes

• Add year-first date and commit SHA to last-slds-markup-review in package.json and push.
• Request a review of the deployed Heroku app by the Salesforce UX Accessibility Team.
• Add year-first review date, and commit SHA, last-accessibility-review, to package.json and push.
• While the contributor's branch is checked out, run npm run local-update within locally cloned site repo to confirm the site will function correctly at the next release.

[welcome]

Thanks for opening this pull request! 💯

This is a community-driven project, and we can't do it without your participation. Please check out our contributing guidelines and review the Contributor Checklist if you haven't already, to make sure everything is squared away. TravisCI will take about 10 minutes to run through the same items that are on the Contributor checklist with a pass/fail check below. Please fix any issues that cause TravisCI to fail or ask for clarification--we try, but sometimes the errors can be unclear.
A maintainer will try to respond within 7 days. If you haven’t heard anything by then, please bump this thread.

[salesforce-cla]

Thanks for the contribution! It looks like @jacobroschen is an internal user so signing the CLA is not required. However, we need to confirm this.

[jamesward]

@jacobroschen I've invited you to the org: https://github.com/salesforce

Once accepted, refresh the CLA bot: https://cla.salesforce.com/status/salesforce/design-system-react/pull/1651

[jacobroschen]

Thanks @jamesward! That was easier than I expected.

[futuremint]

Some suggestions on leveraging lodash a little more.

[futuremint]

Looks like my code suggestions introduced lint errors 😁 .

[welcome]

Congrats on merging your first pull request to Design System React! 🎉

On behalf of Salesforce's customers, partners, product specialists and employees, we would like offer sincere thanks and appreciation for helping make our user experience better. We look forward to working with you more in the future.

This definitely calls for a high five!