fix: use testify instead of t.Fatal or t.Error in client package (part 1)

[mmorel-35]

Description

This uses testify instead of testing for t.Fatal or t.Error calls in client package

Related to #18972

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mmorel-35
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[k8s-ci-robot]

Hi @mmorel-35. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.76%. Comparing base (2b32307) to head (1d5a9bd).

Additional details and impacted files

see 21 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #18967      +/-   ##
==========================================
- Coverage   68.78%   68.76%   -0.02%     
==========================================
  Files         420      420              
  Lines       35629    35629              
==========================================
- Hits        24506    24499       -7     
- Misses       9700     9706       +6     
- Partials     1423     1424       +1     

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[ahrtr]

/ok-to-test

[ivanvc]

/retest

[ivanvc]

Question, @mmorel-35. How are you planning on splitting these pull requests? I want to understand it so that I can deliver a proper review :)

[mmorel-35]

I'm grouping PR per package/subpackage and priorizing t.Fatal replacement.
I try to limit the number of modification to less than 100 or 200 lines so it stays reviewable