Add Windows WSL [Ubuntu] Agent Shell Support for IntelliJ

[GabeChurch]

Currently Continue agents only support using powershell execution in IntelliJ -- one of the more powerful abilities of IntelliJ that is widely used is "projects stored in and utilizing the Ubuntu (Windows Subsytem for Linux)".

When opening projects in WSL the terminal and dependencies automatically switch over to that Ubuntu environment -- which is again quite useful and powerful for development. Unfortunately as of now, when projects are a visible WSL filesystem "\wsl$\Ubuntu\home\user\something" the continue agents just revert to a random powershell location for execution which makes it quite difficult to use agents in projects that are based in Ubuntu using the WSL.

I went ahead and made a pull request to add this feature, with a new runnable test using the existing Intellij plugin launch system for development -- and verified there is no impact on VSCode use cases, and macos IntelliJ.

If I could get some eyes to help review it would be great to get merged in! There are quite a few mentions of others seeking this feature as well.
#12442