test: add new startNewREPLSever testing utility

[dario-piotrowicz]

This PR adds a new testing utility called startNewREPLSever which simply starts a new repl server that can be used for testing.

The reasoning for proposing this change are to reduce unnecessary code repetition (notice that the PR is net removing more than 450 lines of code¹) and to also provide some consistency on how repl server are tested.

Currently in tests when a new repl server gets started some input/output streams need to be passed to it, sometimes they are implemented via new stream.PassThrough(), some other times (more commonly) via new ArrayStream(), sometimes a single stream is passed both as the input and output, sometimes different streams are passed instead.
In most cases (as far as I can tell) there isn't a specific reason as to why an implementation has been chosen or not. startNewREPLSever removes this variation by adopting what looked to me like the most commonly used implementation aspects.

Another nice thing is that startNewREPLSever helps with variable name consistency. Currently when a test repl server is started it is stored in a variable which name can be r, replServer, server or testMe. Input streams can be input, putIn or inputStream. Output streams can be output, putIn or outputStream. (I am likely forgetting some variation too). startNewREPLSever consistently refers to these values respectively as replServer , input and output.

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Please note that my PR is not replacing all repl server starts in tests with startNewREPLSever, mainly because sometimes that is not helpful (for example when testing the repl constructor default values) or because it would require some involved refactoring (and I think that this PR is pretty big as it is 😅, if this lands I can also see as a followup if startNewREPLSever could, be used in a few other tests as well)

Footnotes

1. The output accumulation logic is re-implemented multiple times as well as the error domain on error handler logic. ↩

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.41%. Comparing base (3625623) to head (9112a5c).
⚠️ Report is 46 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59964      +/-   ##
==========================================
- Coverage   88.41%   88.41%   -0.01%     
==========================================
  Files         703      703              
  Lines      207398   207419      +21     
  Branches    39987    39997      +10     
==========================================
+ Hits       183374   183390      +16     
- Misses      15995    15998       +3     
- Partials     8029     8031       +2     

see 28 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/69333/

[addaleax]

Landed in 9ac571d