Not sure if it's used because it can return undefined, but it's
there now!

It looks like before, the ISetTerminalLAyoutInfoArgs and
IGetTerminalLayoutInfoArgs were part of the terminal interface, but now they're
just interfaces so this commit fixes the imports to get them from
vs/platform/terminal/common/terminalProcess.

It looks like they moved a bunch of terminal-related files around.

This only fixes the imports.

It doesn't mean much until we persist terminals though, I think.

We used this to run vscodevim in the browser but it now has a version
that is able to run as a VS Code web extension. This does require an
update to our marketplace, however.