AC-15237: 'As low as' price label is shown for configurable products with single option

Updated "As low as" label for configurable product with single option. Added Unit and Integration test coverage

Author: sumesh-GL

app/code/Magento/ConfigurableProduct/Pricing/Price/ConfigurableRegularPrice.php

@@ -253,7 +253,7 @@ public function isChildProductsOfEqualPrices(SaleableInterface $product): bool
             }
         }
 
-        if ($saleableChildrenCount <= 1 || $firstFinal === null || !$allEqual) {
+        if ($saleableChildrenCount < 1 || $firstFinal === null || !$allEqual) {
             $product->setData($memoKey, false);
             $this->equalFinalPriceCache[$cacheKey] = false;
             return false;