[common-artifacts] Revise `venv_2_12_1` to versionless name

[seanshpark]

Current name for python virtual env folder, prepared in common-artifacts, uses venv_2_12_1 which has version in the name.
As to upgrade TensorFlow version, we may have to choose different ones depending on Ubuntu version.
This name is used in several other modules that require python execution environment, so updating requires labor.

So, I'd like to remove version name in the folder.

• user module don't need to have updates afterwards
• we can have different TF version for each Ubuntu
• but... I can't recall if there was any problem ...

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• from [compiler] Support Ubuntu24.04 with latest packages #15226

[seanshpark]

Steps

• common-artifacts, add overlay/venv
• for other modules, revise to use new overlay/venv
• common-artifacts, remove overlay/venv_2_12_1