Make the time tracking sidebar widget and report more reactive

What does this MR do and why?

This is a follow-up of !88122 (merged) and related to #364500.

When adding the possibility to remove a timelog from the report using a button, I ended up manually updating the apollo cache in order to remove the timelog from the frontend data (thus updating the report). This led to some problems:

• it was inefficient
• the data on the time tracking widget on the sidebar was not automatically updated so I had to "brute force" an update when the report closed

This MR improves on that, taking advantage of apollo smart queries.

Screenshots or screen recordings

Registrazione_schermo_2022-08-12_alle_08.45.41

How to set up and validate locally

It should be sufficient to the if the time tracking widget and the report are updated correctly when:

• on Issues and Merge Requests
  • adding a timelog with the /spent quick action
  • removing a timelog from the time tracking report
• on Milestones and Epics
  • the data should only be visible on the sidebar
  • the report should not be avaiable

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.