`shellStartup` does not activate when in WSL

[karthiknadig]

Repro steps:

1. From a WSL bash prompt
2. Create a project folder with a python file and a venv.
3. Start VS Code in that repo.
4. Notice that the venv is detected and selected.
5. Changing the python-envs.terminal.autoActivationType from shellStartup to off or vice versa has no effect.

This happens because, .bashrc could have been previously updated with VSCODE_BASH_ACTIVATE as script variable, now it is VSCODE_PYTHON_BASH_ACTIVATE we need to check this and update it.

[anthonykim1]

Edit: Resolved in Fix where activation goes missing after user modifying rc scripts #880

Did not have to launch via wsl, was able to repro in mac.

[karthiknadig]

The issue now in WSL is that it still uses command activation and not shell activation. Likely due to #882