Added timelogs pagination and total time spent retrieval

What does this MR do and why?

This MR expands the timelogs connection type to also expose:

• the count of timelogs matching the search terms
• the total amount of time spent for timelogs matching the search terms

Screenshots or screen recordings

N.A.

How to set up and validate locally

1. Log some spent time on an issuable
2. Run this GraphQL query and make sure the returned values are right:

   query {
     currentUser {
       timelogs {
         totalSpentTime
         count
       }
     }
   }

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.