added detailed file with timelogs to issue export

What does this MR do?

Provides second file to issue export that contains information about all time tracking records for every issue. Added three fields about time tracking records:

• time spent — individual time tracking value
• time spent by — username who recorded the time spent value
• time spent on — datetime where time was spent entered by user in format YYYY-MM-DD HH::MM:SS UTC

Example of output you can see on screenshot.

Screenshots

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #3803