[google_maps_flutter] Use super parameters in more places in examples

[srawlins]

Changes to the Dart analyzer will catch more situations where super-parameters should be used, for the use_super_parameters lint rule. We need to clean up this example code before it can land.

Work towards dart-lang/sdk#58729

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[flutter-dashboard]

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[gemini-code-assist]

Code Review

This pull request updates numerous example files across the Google Maps Flutter packages to utilize the super.key constructor parameter shorthand. A review comment suggests moving the super.key parameter to the beginning of the parameter list in advanced_marker_icons.dart to maintain consistency with Flutter conventions and other constructors in the repository.