Small improvements of the task terminal spawn behavior (#9399)

* Add a `reveal: always|never` field in task definitions from tasks.json
, allowing to customize task terminal behavior on spawn
* Ensure reveal: always reveals the terminal even if the old task is
already running


Release Notes:

- Added a `reveal: always|never` (`always` is a default) field in task
definitions from tasks.json , allowing to customize task terminal
behavior on spawn

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Co-authored-by: Piotr Osiewicz <piotr@zed.dev>