Switch to aws-sdk-go-v2

[lebauce]

Requirements

All new code should be covered with tests, documentation should be updated. CI should pass.

Description of the Change

This PR switches aptly from using aws-sdk-go to aws-sdk-go-v2, the new Go SDK for AWS.
Among many improvement, one is that the endpoints are not stored in global variables, freeing
some memory.

Checklist

• unit-test added (if change is algorithm)
• functional test added/updated (if change is functional)
• man page updated (if applicable)
• bash completion updated (if applicable)
• documentation updated
• author name in AUTHORS

[codecov]

Codecov Report

Merging #1226 (fc0b4b9) into master (322e5c1) will decrease coverage by 0.03%.
The diff coverage is 59.03%.

@@            Coverage Diff             @@
##           master    #1226      +/-   ##
==========================================
- Coverage   65.96%   65.94%   -0.03%     
==========================================
  Files         143      143              
  Lines       16188    16178      -10     
==========================================
- Hits        10679    10668      -11     
  Misses       4756     4756              
- Partials      753      754       +1     

Files	Coverage Δ
s3/public.go	55.95% <59.03%> (-1.57%)	⬇️

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