Revert terminal memory leak fixes (#23636)

New mechanism had introduced the following regressions:

* Windows tasks are not registering child exit properly, sometimes
getting stuck in dirty state (even with
https://github.com/zed-industries/zed/pull/23631):


https://github.com/user-attachments/assets/6d406f17-aa76-4012-9c3b-be72d6d5beae

* Overall, the terminal editing started to feel more sluggish, esp. in
regards to deletions (ctrl-w and backspace), tested on macOS:


https://github.com/user-attachments/assets/3a69fe2e-e394-45e8-8f51-0f5ac396cb24


Release Notes:

- N/A