test: update startCLI to set --port=0 by default

[dario-piotrowicz]

update the startCLI debugging testing utility to set by default the port to use to 0 (i.e. a random port)

---

To me this sounds like the most appropriate default behavior since:

• setting the port to 0 is the general correct behavior and most startCLI calls currently indeed do that
• generally forgetting to set the port to 0 would most likely lead to issues down the line that would however not be immediately apparent such as flakiness (i.e. it's easy to forget and doing so can cause issues later on)
  (for example see: test: add missing port=0 arg in test-debugger-extract-function-name #58977)
• when a specific port should be used that's clear based on the test and the caller would in any case need to already factor that in in the startCLI call, if they didn't the test would always fail (instead of generally passing but with potential flakes)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.06%. Comparing base (0992d28) to head (bee555a).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59042      +/-   ##
==========================================
- Coverage   90.06%   90.06%   -0.01%     
==========================================
  Files         641      645       +4     
  Lines      188846   189130     +284     
  Branches    37049    37099      +50     
==========================================
+ Hits       170087   170342     +255     
+ Misses      11476    11465      -11     
- Partials     7283     7323      +40     

see 48 files with indirect coverage changes

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