Convert Sprint Template Button to 'Spinning' Loading Button

[mikhael28]

Summary

Right now, when creating/updating a sprint template, the button doesn't really show that it is in progress towards loading the response of the API request. Change the button to have a spinning indicator similar to other buttons in the code-base.

Motivation

We want to give our users a good user experience, and a part of that entails letting them know that their actions are in fact processing.

Additional context

You can view this GIF to see the page itself with button towards the top right.