Summary

Fixes #34002.

When the client aborts an HTTP request before res.end() runs, the
server-side socket fires its 'close' event, which calls
emitCloseNT(res) on the in-flight ServerResponse. emitCloseNT sets
destroyed = true / _closed = true and emits 'close'. The deferred
res.end() then schedules onFinish via the _send callback,
and onFinish only checked socket._hadError — that flag is not set on
the abort path in Deno, so 'finish' was emitted after 'close'.

Node emits only 'close' in that scenario.

This PR adds a destroyed guard to onFinish so the response stops
emitting 'finish' once it has already been destroyed (either via the
response or its socket).

Reproducer (from #34002)

const http = require('http');

let client;
let count = 0;

const server = http.createServer((req, res) => {
  res.on('finish', () => { console.log('finish'); count++; });
  res.on('close', () => { console.log('close'); count++; });

  client.abort();

  setImmediate(() => {
    setImmediate(() => {
      res.end('ok');
      setImmediate(() => {
        server.close(() => { console.log('event count:', count); });
      });
    });
  });
});

server.listen(0, () => {
  client = http.get(`http://127.0.0.1:${server.address().port}`);
  client.on('error', () => {});
});

Before (Deno 2.7.14 release):

finish
close
event count: 2

After (Node, and Deno with this fix):

close
event count: 1

Test plan

• Added tests/unit_node/http_test.ts regression test
  "[node/http] ServerResponse does not emit 'finish' after client abort"
• All existing ServerResponse tests still pass (deno test -A tests/unit_node/http_test.ts --filter "ServerResponse")
• tools/format.js clean
• tools/lint.js --js clean

Closes bartlomieju/orchid-inbox#47