Add main_thread metrics added in 6.2

[artificial-aidan]

Main thread cpu time was added in 6.2

https://raw.githubusercontent.com/antirez/redis/6.2/00-RELEASENOTES

[coveralls]

Pull Request Test Coverage Report for Build 1487

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.009%) to 92.024%

---

Totals
Change from base Build 1482:	0.009%
Covered Lines:	1673
Relevant Lines:	1818

---

💛 - Coveralls

[codecov]

Codecov Report

Merging #619 (c3a0929) into master (a8f5b9c) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #619      +/-   ##
==========================================
+ Coverage   88.06%   88.07%   +0.01%     
==========================================
  Files          16       16              
  Lines        1810     1812       +2     
==========================================
+ Hits         1594     1596       +2     
  Misses        145      145              
  Partials       71       71              

Impacted Files	Coverage Δ
exporter/exporter.go	91.93% <100.00%> (+0.03%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a8f5b9c...c3a0929. Read the comment docs.

[oliver006]

👍

Thanks for the PR!