Integrate AdMob reward verification flow in adapter

[polmiro]

Checklist

• If applicable, unit tests
• If applicable, create follow-up issues for purchases-ios and hybrids

Motivation

The AdMob adapter reward verification APIs are scaffolded, and core reward verification result plumbing is available in :purchases. This PR wires the adapter callback flow end-to-end so AdMob reward callbacks can return deterministic verification outcomes now, while keeping full polling/retry orchestration out of scope for a follow-up PR.

Description

• Connects the AdMob reward verification service locator to Purchases lifecycle registration.
• Adds the AdMob reward verification poller and maps core reward verification results into adapter RewardVerificationResult values.
• Stores per-ad client transaction IDs on enableRewardVerification() and consumes that state when AdMob reports a reward.
• Uses a lifecycle-owned RewardVerificationManager to own state, verification scope, cleanup, and main-thread callback delivery.
• Fails safely with RewardVerificationResult.failed when reward verification show overloads are used without prior enableRewardVerification() or when runtime state is unavailable.
• Treats PENDING, UNKNOWN, and backend errors as failed results for now; retry/backoff orchestration remains out of scope.
• Keeps AdMob adapter callback delivery on the main thread and trusts AdMob to invoke the reward callback once per show.
• Adds focused unit coverage for locator registration and poller result mapping; show behavior coverage remains Robolectric-based.

Out of scope in this PR:

• polling loops
• retries/backoff
• timeout orchestration

---

Note

Medium Risk
Adds new asynchronous reward-verification flow (lifecycle hooks, background polling, main-thread callback delivery) that affects rewarded ad showing behavior and introduces new failure modes if misconfigured.

Overview
Implements the previously-scaffolded AdMob reward verification APIs: enableRewardVerification() now installs per-ad client transaction IDs and show() overloads now invoke a verification pipeline instead of throwing NotImplementedError, with callbacks delivered on the main thread.

Adds a lifecycle-owned RewardVerificationManager/runtime that hooks into a new public PurchasesLifecycle registration API to create/cancel a verification coroutine scope, track ad→transaction IDs (via WeakHashMap), and fail-safe to RewardVerificationResult.failed when setup/state is missing.

Introduces a Poller that calls core awaitGetRewardVerificationResult and maps core statuses into adapter results (treating PENDING/UNKNOWN/errors as failed for now), plus unit/Robolectric coverage for lifecycle registration, polling mapping, placement override behavior, and cancellation handling.

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[tonidero]

Right now, just concerned a bit with the static nature of the state we are holding... Trying to think of ways we can bound it to the purchases instance at least...

[polmiro]

This is pretty the same as PurchasesOrchestrator.dispatch but I was not sure if the wiring was worth while. Perhaps this helper can be promoted to core.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (admob-reward-verification-locator-split@2b0b876). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...evenuecat/purchases/PurchasesLifecycleListeners.kt	0.00%	2 Missing ⚠️

Additional details and impacted files

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##             admob-reward-verification-locator-split    #3468   +/-   ##
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