[ISSUE-520] Pool gzip compressor and buffer used in gzip writer

[pakio]

Description

Changed to pool gzip.Writer object and bytes.Buffer object used for gzip compression, for the better performance.

Issues Resolved

Closes #520

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[pakio]

I will update changelog once the change is finalized.
Also I'm not very sure how can I address the error in the Lint check, it seems like detecting error somewhere I didn't updated.

[dblock]

Looks good. Add to CHANGELOG, + see some asks below. Iterate to green.

[dblock]

Is this code copied from open source Elasticsearch client or is this new? If it's new, you don't need to reproduce the "Licensed to ES" part of the license.

[dblock]

Maybe generate a different/random/based on i body every time? Feels like a missed opportunity :)

[dblock]

If the compressor is a noop and just returns the same string, these tests pass.

1. Add a test that compressed data is different and smaller than the original data.
2. Add a test that decompressing a random buffer returns the expected errors.
3. Add a test that compresses data, then compresses it again, and decompresses it twice to get to source, ensuring nothing is lost.

[dblock]

I will update changelog once the change is finalized. Also I'm not very sure how can I address the error in the Lint check, it seems like detecting error somewhere I didn't updated.

Rebase, we may have fixed this elsewhere since the main build is green.

[codecov]

Codecov Report

Attention: Patch coverage is 83.87097% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 66.21%. Comparing base (06a6dc8) to head (0d39036).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #521      +/-   ##
==========================================
+ Coverage   57.29%   66.21%   +8.92%     
==========================================
  Files         315      364      +49     
  Lines        9823     8587    -1236     
==========================================
+ Hits         5628     5686      +58     
+ Misses       2902     1589    -1313     
- Partials     1293     1312      +19     

Flag	Coverage Δ
integration	59.53% <83.87%> (+8.69%)	⬆️
unit	81.66% <83.87%> (+68.82%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
opensearchtransport/opensearchtransport.go	86.57% <83.33%> (+1.41%)	⬆️
opensearchtransport/gzip.go	84.00% <84.00%> (ø)

... and 249 files with indirect coverage changes

[pakio]

oh I was about to send some message regarding the change. thanks you @dblock for your review and merging the PR!

[dblock]

Good work @pakio, thank you!