feat(payments): StoreKit v2 + Google Billing v8

[NathanWalker]

Reworks the legacy payment setup to be simpler to use while also using all latest SDKs.

Example Usage

import { Payment, Product } from '@nativescript/payments'

const payment = new Payment();
payment.onPurchaseUpdate = (purchases, error) => {
  if (error) {
    console.error(`🛑 Purchase Update Error: ${error} 🛑`);
  } else {
    console.log(`🟢 Purchase Update: ${purchases.length} items 🟢`);
    purchases.forEach((transaction) => {
      switch (transaction.state) {
        case 'pending':
          transaction.finish();
          break;
        case 'purchased':
          console.log(`🟢 Purchase Update: ${JSON.stringify(transaction.receiptToken)} 🟢`);
          break;
      }
    });
  }
};
payment.onReady = async () => {
  try {
    console.log('🟢 Payment System Ready 🟢');
    const purchases = await payment.fetchPurchases();
    console.log(`🟢 Fetched previous ${purchases.length} In App Purchase Items 🟢`);

    const products = await payment.fetchProducts(['io.nstudio.iapdemo.coinsfive', 'io.nstudio.iapdemo.coinsone', 'io.nstudio.iapdemo.coinsonethousand'], 'inapp');

    console.log("here's the products!", products)
  } catch (error) {
    console.error(`🛑 Error: ${error} 🛑`);
  }
};

function buyItem(item: Product) {
  payment.purchaseProduct(item);
}

These changes modernize the payments plugin, simplify its usage, and remove a significant amount of legacy and abstraction code in favor of a more direct and maintainable API.

[edusperoni]

I have some pending changes for billing 8 because it includes API changes. Let's chat about it this week.

Also I don't understand why move all the logic to native, as it's pretty straightforward in JS