src: use BaseObjectPtr in StreamReq::Dispose

Allow the AsyncWrap to be properly detached.

Extracted from the [QUIC PR](https://github.com/nodejs/node/pull/32379

).

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/33102
Refs: https://github.com/nodejs/node/pull/32379/files?file-filters%5B%5D=.bat&file-filters%5B%5D=.gyp&file-filters%5B%5D=.gypi&file-filters%5B%5D=.h&file-filters%5B%5D=.md&file-filters%5B%5D=.py&file-filters%5B%5D=.sh&file-filters%5B%5D=No+extension&file-filters%5B%5D=dotfile#r409084763


Reviewed-By: Anna Henningsen <anna@addaleax.net>