FEA-3240: Support Dart v3

[matthewnitschke-wk]

FEA-3240

I recently discovered that analyzer v5.13.0 can successfully analyze dart 3 code, which in relation means that scip-dart can run on dart3 code

This pr updates the upper bound of the scip-dart cli to allow indexing using any dart version above 2.19.6, and below dart v4

This pr also adds a special snapshot project just for these dart3 features. Reviewing the results of that snapshot file should verify dart 3 features ran on an analyzer v5.13

The previous "dart 3 support branch" has now become the analyzer v6 branch: #68, since this bumps the required lower bound up to dart 3, it will need to stay in draft state

[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.

[isaacharrisholt]

Is there anything I can do to help get this in? Dart 3 has been out for a while now, and a fair few projects have started moving over.