Make NewClientWithEnvProxy Deprecated

[Hash2049]

No description provided.

[gmlewis]

Sorry I wasn't clear before.

I would like to get a solution that addresses the earlier problems mentioned here:
#2898 (comment)
before deprecating NewClientWithEnvProxy.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.21%. Comparing base (2b8c7fa) to head (f70b041).
Report is 203 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3393      +/-   ##
==========================================
- Coverage   97.72%   92.21%   -5.51%     
==========================================
  Files         153      173      +20     
  Lines       13390    14770    +1380     
==========================================
+ Hits        13085    13620     +535     
- Misses        215     1060     +845     
  Partials       90       90              

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