refactor(csv): rename arguments, variables and loop

[timreichen]

• renames opt to options argument
• ~renames fullLine to line and line to currentLine~
• ~renames parseField to currentLineLoop~

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.81%. Comparing base (ee46006) to head (541a8b5).

Files	Patch %	Lines
csv/_io.ts	93.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5297 +/- ## ======================================= Coverage 95.81% 95.81% ======================================= Files 458 458 Lines 37890 37892 +2 Branches 5567 5568 +1 ======================================= + Hits 36304 36306 +2 Misses 1546 1546 Partials 40 40 ```

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[kt3k]

renames fullLine to line and line to currentLine renames parseField to currentLineLoop

I don't see the point of these renames. Can you revert these changes?

[timreichen]

renames fullLine to line and line to currentLine renames parseField to currentLineLoop

I don't see the point of these renames. Can you revert these changes?

I think it is weird to have an assignment which then is stored in another variable because the former is mutated. How about

let fullLine = this.#readLine();
...
let line = fullLine;