added support for multiple tenants in plugin

[Subhash703]

Build Time Changes :

**Android : **
In android/build.gradle ext block add clientConfigs instead of clientId

clientConfigs = [
    <clientId1>: {
        return [
                tenantName: "<tenant_name1>"
        ]
    },
    <clientId2>: {
               tenantName: "<tenant_name2>"
    }
]

IOS
Create a MerchantConfig.json file in the folder where your app's Podfile is present and add your clientConfigs there.

{
  "clientConfigs": {
      "testlatamprod13": {
          "tenantName": "<tenantName1>"
      },
      "<clientId2>": {
          "tenantName": "<tenantName2>"
      }
  }
}

Dart
Merchant must create HyperInstance separately by calling below method on HyperSDK.

hyperSDK.createHyperServicesWithTenantId("<tenantName>", "<clientId>");