Add close_workflow button action

[facumenzella]

Summary

Ports purchases-android#3453 to iOS.

Supports the backend `close_workflow` button action for Paywalls V2 so it dismisses the entire paywall/workflow, including from nested contexts such as sheets, without introducing a source-breaking public API change.

Changes

• Keeps `PaywallComponent.ButtonComponent.Action` unchanged as a public enum
• Preserves backend `"close_workflow"` via an internal SPI marker (`isCloseWorkflowAction`) on `ButtonComponent`
• Maps that marker to the internal `ButtonComponentViewModel.Action.closeWorkflow`
• Threads a dedicated top-level `closeWorkflowAction` separately from contextual `onDismiss`, so `close_workflow` never reuses workflow back-navigation behavior
• Uses that dedicated close action from nested contexts, including sheets
• Logs a warning if `close_workflow` is triggered without a handler
• Unit tests:
  • Decode/encode round-trip and isCloseWorkflowAction flag (testCloseWorkflowDecoding, testCloseWorkflowRoundTripsThroughEncoding)
  • Equality/hash regression: close_workflow and navigate_back buttons with the same .action value are distinct via isCloseWorkflowAction (testCloseWorkflowAndNavigateBackButtonsAreNotEqual)
  • ViewModel mapping: decoded close_workflow component maps to .closeWorkflow action with correct interaction value (ButtonComponentViewModelMappingTests)

Verification

• `swift build`
• `swift test`
• `bundle exec fastlane run_api_tests`

---

Note

Medium Risk
Adds a new workflow dismissal path and custom decoding/encoding to preserve a backend-only action; mistakes could cause buttons to dismiss the wrong layer (step vs whole workflow) or regress component equality/telemetry.

Overview
Adds support for the backend close_workflow button action in Paywalls V2 so a button can dismiss the entire workflow/paywall (even from nested contexts like sheets) rather than performing step back-navigation.

This preserves API compatibility by decoding "close_workflow" as public .navigateBack while storing an internal isCloseWorkflowAction flag, mapping it to a new internal view-model action (.closeWorkflow), and threading a top-level closeWorkflowAction through the SwiftUI environment (with warning logs when unhandled). Tests cover decoding/round-tripping, equality/hash behavior, interaction value mapping, and project integration.

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