feat: add avoid-top-level-members-in-tests

[incendial]

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix
[X] New rule
[ ] Changes an existing rule
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Implements: dart-lang/linter#1258

[github-actions]

Dart Code Metrics unused files report of dart_code_metrics. ✅

Summary

• Scanned package folders: bin, example, lib
• No unused files found! ✅

[github-actions]

Dart Code Metrics analyze report of dart_code_metrics. ✅

Summary

• Scanned folders: bin, example, lib, test

• Total scanned files: 457

• Total lines of source code: 8002

• Total classes: 316

• Average Cyclomatic Number per line of code: 0.35

• Average Source Lines of Code per method: 6

• Total tech debt: 1366.0 hours

• Found issues: 6 ⚠

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@b6a3946). Click here to learn what that means.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #920   +/-   ##
=========================================
  Coverage          ?   87.45%           
=========================================
  Files             ?      304           
  Lines             ?     6266           
  Branches          ?        0           
=========================================
  Hits              ?     5480           
  Misses            ?      786           
  Partials          ?        0           

Impacted Files	Coverage Δ
...c/analyzers/lint_analyzer/rules/rules_factory.dart	71.42% <ø> (ø)
...n_tests/avoid_top_level_members_in_tests_rule.dart	100.00% <100.00%> (ø)
...list/avoid_top_level_members_in_tests/visitor.dart	100.00% <100.00%> (ø)

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[sonarcloud]

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0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

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