refactor: migrate SendStream to ES6 classes

[mon-jai]

Checklist

• run npm run test and npm run benchmark (There is no benchmark script in this package)
• tests and/or benchmarks are included
• documentation is changed or added (There are no changes affecting the API)
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

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This pull request migrates SendStream to ES6 classes.

Note

• I have done my best to maintain the original code formatting.
• All tests and lint checks pass successfully after implementing these changes.

Changes Made

• Migrated SendStream to ES6 classes.
• Replaced || with ?? (nullish coalescing operator) wherever appropriate.
• Removed || false which was redundant ((etag && ifRange.indexOf(etag) !== -1) || false ➡️ (etag && ifRange.indexOf(etag) !== -1)).

Changes to Consider

• Utilize ES2022 private properties for private methods and properties (_acceptRanges ➡️ #acceptRanges, hasTrailingSlash() ➡️ #hasTrailingSlash()).

[mon-jai]

The change is minimal when whitespace changes are hidden.

[gurgunday]

It looks fine but some maintainers do not like the idea of refactoring to classes for no reason, which is understandable as it may introduce subtle bugs

[mcollina]

I'm -1 for that reason. You can also see a Proxy creeping in to be feature compatible.

[gurgunday]

Closing as it's no longer feasible to extend Stream and do such a refactor

But thanks for the effort