Update dependency pigeon to v12

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
pigeon	dev_dependencies	major	11.0.1 -> 12.0.0

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Release Notes

flutter/packages (pigeon)

v12.0.0

• Adds error handling on Flutter API methods.
• Breaking Change [kotlin] Flutter API methods now return Result<return-type>.
• Breaking Change [swift] Flutter API methods now return Result<return-type, FlutterError>.
• Breaking Change [java] Removes Reply class from all method returns and replaces it with Result.
  • Changes required: Replace all Reply callbacks with Result classes that contain both success and failure methods.
• Breaking Change [java] Adds NullableResult class for all nullable method returns.
  • Changes required: Any method that returns a nullable type will need to be updated to return NullableResult rather than Result.
• Breaking Change [java] Renames Host API setup method to setUp.
• Breaking Change [objc] Boxes all enum returns to allow for nil response on error.
• Breaking Change [objc] Renames <api>Setup to SetUp<api>.

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Configuration

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[renovate]

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