Integrate order calculation API to FE

[shreyanshdwivedi]

Is your feature request related to a problem? Please describe.

Currently, we are implementing a new API on the server to handle tax and discount calculation for an order. Once it is merged on the server, FE should be changed accordingly
Server PR - fossasia/open-event-server#6366

Describe the solution you'd like

When user selects tickets and applies discount code (or not) and hit Order Now button, the data should be sent to /orders/calculate-amount to fetch calculated response and use it to display on FE

Additional context

Will start working on it

[mariobehling]

Implemented during orders rewrite.