http: fix crash for sync write errors during header parsing

Fix a crash that occurs when `parser.finish()` is called during
`parser.execute()`. In this particular case, this happened because
a 100 continue response is a place in which `.end()` can be called
which can in turn lead to a write error, which is emitted
synchronously, thus inside the outer `parser.execute()` call.

Resolve that by delaying the `parser.finish()` call until after
the `parser.execute()` call is done.

This only affects v12.x, because on later versions, errors are not
emitted synchronously.

PR-URL: #34251
Fixes: #15102
Fixes: #34016
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

lib/_http_client.js

@@ -431,8 +431,12 @@ function socketErrorListener(err) {
 
   const parser = socket.parser;
   if (parser) {
-    parser.finish();
-    freeParser(parser, req, socket);
+    // Use process.nextTick() on v12.x since 'error' events might be
+    // emitted synchronously from e.g. a failed write() call on the socket.
+    process.nextTick(() => {
+      parser.finish();
+      freeParser(parser, req, socket);
+    });
   }
 
   // Ensure that no further data will come out of the socket