Enable toolchain venv in new terminals (#21388)

Fixes part of issue #7808 

> This venv should be the one we automatically activate when opening new
terminals, if the detect_venv setting is on.

Release Notes:

- Selected Python toolchains (virtual environments) are now automatically activated in new terminals.

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Co-authored-by: Piotr Osiewicz <[email protected]>

Author: sn1c