[Feature Request]: Clean support for strict dependency managers (e.g., pnpm default)

[ryanbliss]

There are lots of issues with strict dependency settings in Live Share, since we use child packages of the fluid-framework package in Live Share. With non-strict settings (default for npm and yarn), node_modules is flat, meaning that you can access child dependencies of packages in your package.json even though you don't explicitly declare it in your package.json. But when in strict, you cannot do that, and thus they need to resolve those manually in pnpm config files. We should try to clean this up in Live Share V2.