v2 fastify/busboy hangs

@LinusU I noticed that you are using @fastify/busboy instead of original one for streaming variant 2.x.x. I faced hangs during mixed fields+file multipart upload and I found out that fastify implementaion is buggy and doesn't properly handle streams which results in hangs (end/finish/error/close not triggered). When I switched to original busboy, it just works and all events are triggered as expected (I tried it also without multer mw). It is hard to provide reproducible example as there are too many variables (nginx/apache, browser, multipart content etc), but I wanted to just pointed this out as it deserves your attention. Thanks.

P.S I also noticed that lts uses some really prehistoric version of busboy. Maybe it would be worth it to bump version.