Make example a separate pkg to remove over_react

[robbecker-wf]

Motivation

The dependency on over_react isn't necessary since it is only used in the example subdir.

Changes

Move the examples to example/web dir and make the example dir a separate package.
Remove the over_react dependency from the root.

Also got CI running on Dart 2.19 and added excludes to the root analysis and dependency validator so it didn't complain that over_react is still needed.

QA Checklist

• Tests were updated and provide good coverage of the changeset and other affected code
• Manual testing was performed if needed
  • Steps from PR author:
  • Anything falling under manual testing criteria outlined in CONTRIBUTING.md

Merge Checklist

While we perform many automated checks before auto-merging, some manual checks are needed:

• A Frontend Architecture member has reviewed these changes
• There are no unaddressed comments - this check can be automated if reviewers use the "Request Changes" feature
• For release PRs - Version metadata in Rosie comment is correct

[aviary-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure
• Verify aviary.yaml coverage of security relevant code

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Questions or Comments? Reach out on Slack: #support-infosec.

[akshaybhardwaj-wk]

LGTM

[robbecker-wf]

QA+1 CI passes @Workiva/release-management-p

[rmconsole-wf]

+1 from RM