Rename internal SSV symbols, URL and metric to RewardVerification (#6667)

* Rename internal AdMobSSV symbols, URL and metric to RewardVerification

Renames the internal AdMobSSV* types and SPI introduced in #6641 to
RewardVerification* so the wording stays adapter-agnostic. Also renames
the backend URL path and the client-side metric to match, so the SPI is
provider-agnostic end to end.

Renames:
- Sources/Ads/AdMobSSV/ -> Sources/Ads/RewardVerification/
- AdMobSSVPollStatus -> RewardVerificationPollStatus
- RewardVerificationPollStatus.validated -> .verified
- AdMobSSVStatusResponse -> RewardVerificationStatusResponse
- RewardVerificationStatusResponse.Status.validated -> .verified
  (the decoder still accepts the legacy "validated" wire value during
  the rollout window; covered by a new decoder unit test)
- AdMobSSVStatusCallback -> RewardVerificationStatusCallback
- GetAdMobSSVStatusOperation -> GetRewardVerificationStatusOperation
- AdsAPI.getAdMobSSVStatus -> getRewardVerificationStatus
- Purchases.pollAdMobSSVStatus -> pollRewardVerificationStatus
- HTTPRequest.Path.adMobSSVStatus -> .rewardVerificationStatus
- URL path: /ads/admob/ssv/{tx} -> /ads/reward_verifications/{tx}
- Metric name: get_admob_ssv_status -> get_reward_verification_status
- BackendErrorStrings.unknown_admob_ssv_status -> .unknown_reward_verification_status
- Test files, test methods and snapshot artifacts renamed to match.
- Xcode project file references updated in lockstep.

* Drop legacy `validated` wire-value compat in RewardVerification decoder

The `RewardVerificationStatusResponse` decoder was accepting both `"verified"`
and the legacy `"validated"` status from the backend as a backwards-compat
hedge during rollout. The endpoint has not been shipped and the SDK has no
public entry point that polls it yet, so there is no compatibility window to
preserve — the decoder can require `"verified"` outright.

While here, simplify the decoder to look up known cases via
`Status(rawValue:)` instead of a string-literal switch, so adding a future
case can't silently drift from the enum.

Removes the corresponding `testDecodesLegacyValidatedWireValueAsVerified`
test. Existing coverage for `verified`, `pending`, `failed`, and the
`unknown` fallback (with the `Logger.warn` assertion) is unchanged.

* Update Sources/Purchasing/Purchases/Purchases.swift

Co-authored-by: Antonio Pallares <ajpallares@users.noreply.github.com>

* test: assert warning is logged when decoding literal "unknown" status

Address review feedback: cover the case where the backend sends the
literal "unknown" wire value, which still falls through the
unmapped-status branch and should emit a warning.

---------

Co-authored-by: Antonio Pallares <ajpallares@users.noreply.github.com>

Sources/Networking/HTTPClient/HTTPRequestPath.swift

@@ -107,7 +107,7 @@ extension HTTPRequest {
         case postRedeemWebPurchase
         case postCreateTicket
         case isPurchaseAllowedByRestoreBehavior(appUserID: String)
-        case adMobSSVStatus(appUserID: String, clientTransactionID: String)
+        case rewardVerificationStatus(appUserID: String, clientTransactionID: String)
 
     }
 
@@ -195,7 +195,7 @@ extension HTTPRequest.Path: HTTPRequestPath {
                 .appHealthReport,
                 .postCreateTicket,
                 .isPurchaseAllowedByRestoreBehavior,
-                .adMobSSVStatus:
+                .rewardVerificationStatus:
             return true
 
         case .health,
@@ -223,7 +223,7 @@ extension HTTPRequest.Path: HTTPRequestPath {
                 .appHealthReport,
                 .postCreateTicket,
                 .isPurchaseAllowedByRestoreBehavior,
-                .adMobSSVStatus:
+                .rewardVerificationStatus:
             return true
         case .health,
              .appHealthReportAvailability:
@@ -254,7 +254,7 @@ extension HTTPRequest.Path: HTTPRequestPath {
                 .getCustomerCenterConfig,
                 .postCreateTicket:
             return false
-        case .adMobSSVStatus:
+        case .rewardVerificationStatus:
             return true
         }
     }
@@ -268,7 +268,7 @@ extension HTTPRequest.Path: HTTPRequestPath {
                 .health,
                 .appHealthReportAvailability,
                 .isPurchaseAllowedByRestoreBehavior,
-                .adMobSSVStatus:
+                .rewardVerificationStatus:
             return true
         case .getWorkflow,
                 .getOfferings,
@@ -348,8 +348,8 @@ extension HTTPRequest.Path: HTTPRequestPath {
         case let .isPurchaseAllowedByRestoreBehavior(appUserID):
             return "subscribers/\(Self.escape(appUserID))/restore/eligibility"
 
-        case let .adMobSSVStatus(appUserID, clientTransactionID):
-            return "subscribers/\(Self.escape(appUserID))/ads/admob/ssv/\(Self.escape(clientTransactionID))"
+        case let .rewardVerificationStatus(appUserID, clientTransactionID):
+            return "subscribers/\(Self.escape(appUserID))/ads/reward_verifications/\(Self.escape(clientTransactionID))"
         }
     }
 
@@ -411,8 +411,8 @@ extension HTTPRequest.Path: HTTPRequestPath {
         case .isPurchaseAllowedByRestoreBehavior:
             return "post_restore_eligibility"
 
-        case .adMobSSVStatus:
-            return "get_admob_ssv_status"
+        case .rewardVerificationStatus:
+            return "get_reward_verification_status"
         }
     }