[in_app_purchase_android] Add obfuscated profile ID purchase param

[lianshumin]

Adds an optional obfuscatedProfileId parameter to GooglePlayPurchaseParam
and passes it through to Google Play Billing's
BillingFlowParams.Builder.setObfuscatedProfileId().

This keeps the API Android-specific, since setObfuscatedProfileId() is a
Google Play Billing API and has no StoreKit equivalent. Existing behavior is
unchanged because the new parameter is optional.

Fixes flutter/flutter#130128

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[gemini-code-assist]

Code Review

This pull request adds support for passing an obfuscated profile ID (obfuscatedProfileId) in GooglePlayPurchaseParam for the Android in-app purchase implementation, propagating it to the billing flow parameters, and adding a corresponding unit test. The review feedback suggests documenting that obfuscatedProfileId requires applicationUserName to be specified, and updating the unit test to include both parameters for a more realistic scenario.

[stuartmorgan-g]

Thanks for the contribution!

• I followed the version and CHANGELOG instructions, using semantic versioning and the [repository CHANGELOG style]

I don't see this in the PR. Please mark the PR as Ready for Review once this item has been completed.

[gemini-code-assist]

Code Review

This pull request adds support for passing an obfuscated profile ID (obfuscatedProfileId) in GooglePlayPurchaseParam for the Android implementation of the in-app purchase plugin. It updates buyNonConsumable to pass this parameter to the billing flow and adds a corresponding unit test. Feedback suggests adding a unit test to verify that an assertion error is thrown if obfuscatedProfileId is provided without applicationUserName.