APPS-1779 Simple time submission

:koala:

This PR intends to add simple time submission functionality, so the agents can submit time log as a single number which represents how many minutes they spent on the ticket.

/cc @zendesk/quokka 

### SCREENSHOT

### REFERENCE
- [JIRA APPS-1779](https://zendesk.atlassian.net/browse/APPS-1779)

### RISKS
- N/A