fix(res): support raw ArrayBuffer in res.send()

[vaibhavmashal]

Fixes #7362

Description

Previously, passing a raw \ArrayBuffer\ to
es.send()\ fell through the switch statement in \lib/response.js\ to \ his.json(chunk), resulting in {}\ being sent as JSON response rather than binary data.

Solution

• Added a check for \chunk instanceof ArrayBuffer\ in
  es.send().
• Converted raw \ArrayBuffer\ to a \Buffer\ via \Buffer.from(chunk).
• Set \Content-Type: application/octet-stream\ (using \ his.type('bin')) if \Content-Type\ is not already configured, consistent with \Buffer\ and \ArrayBufferView\ handling.
• Added unit tests in \ est/res.send.js\ asserting that
  es.send(new ArrayBuffer(10))\ responds with 10 bytes and \Content-Type: application/octet-stream, while respecting custom content types.

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[krzysdz]

Duplicate of #7363