Support plugins directly registering React components

[aldeed]

Impact: minor
Type: feature

Issue

Previously you had to make a Blaze template to wrap a React component in order to register it for "paymentSettings", "taxSettings", "marketplaceMerchantSettings", or "coreOrderShipmentWorkflow" UI extension.

Solution

Now a plugin can directly register template: "SomeReactTemplate" for these UI areas as long as "SomeReactTemplate" matches how it was registered with the first argument of registerComponent.

Breaking changes

None. Registering a Blaze template name still works, too.

Testing

1. Verify that the affected UI areas still display and function properly with the standard installation.
2. Verify that a React component name can be passed as the template option for at least one of these areas. If you alter an existing plugin to test this, you'll also need to drop the Packages collection and restart since packages that already exist aren't updated on startup.

[kieckhafer]

Looks good. For testing purposes, I swapped the Tax settings Blaze template with a React AccountsDashboard component, worked as it should!

👍