feat(cli): add test for readSocketPath

[jsjoeio]

This PR adds tests for readSocketPath.

TODOs

• extract readSocketPath and export
• fix TS error
• write test for readSocketPath

Fixes N/A

[github-actions]

✨ Coder.com for PR #4284 deployed! It will be updated on every commit.

• Host: https://codercom-a1hd44zbp-codercom.vercel.app/docs/code-server
• Last deploy status: success
• Commit: 703a502
• Workflow status: https://github.com/cdr/code-server/actions/runs/1400378356

[greyscaled]

✔️ looks good to me - just had a question about using a type predicate on ErrnoException

[jsjoeio]

Waiting on #4290

[codecov]

Codecov Report

Merging #4284 (703a502) into main (0100d4c) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #4284      +/-   ##
==========================================
+ Coverage   66.21%   66.29%   +0.08%     
==========================================
  Files          31       31              
  Lines        1619     1620       +1     
  Branches      316      316              
==========================================
+ Hits         1072     1074       +2     
+ Misses        469      468       -1     
  Partials       78       78              

Impacted Files	Coverage Δ
src/node/cli.ts	82.50% <100.00%> (+0.49%)	⬆️
src/node/util.ts	79.23% <100.00%> (ø)

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