Deprecate (and remove) `traverseNodesInDFS`

[pq]

This utility method has been the root of some pathologically bad performance (#58881, #57484) but is not great even in the common case. As a rule, there's always a better way so we should remove it.

• migrate prefer_constructors_over_static_methods from traverseNodesInDFS dart-archive/linter#3747
• migrate prefer_interpolation_to_compose_strings from traverseNodesInDFS dart-archive/linter#3746
• migrate avoid_returning_null from traverseNodesInDFS dart-archive/linter#3744
• migrate unnecessary_lambdas from traverseNodesInDFS() dart-archive/linter#3721
• migrate diagnostic_describe_all_properties from traverseNodesInDFS() dart-archive/linter#3720
• migrate prefer_foreach from traverseNodesInDFS() dart-archive/linter#3719
• migrate cascade_invocations from traverseNodesInDFS() dart-archive/linter#3718
• migrate parameter_assignments from traverseNodesInDFS() dart-archive/linter#3715
• migrate avoid_null_checks_in_equality_operators away from traverseNodesInDFS() dart-archive/linter#3714
• migrate invariant_booleans from using traverseNodesInDFS
• migrate condition_scope_visitor from using traverseNodesInDFS
• migrate leak_detector_visitor from using traverseNodesInDFS

[srawlins]

It would be neat to take a benchmark of the current linter release and the next one to see all of the performance gains we've made.

[srawlins]

Fixed with e1a8a61