In short, this PR adds a 3rd layer to the server compiler. This extra
layer is for marking the modules when re-entering the server layer from
a client component. It is almost identical to the existing server layer
and it should have all the same bundling and runtime behaviors, but it's
still special because it's not allowed to enter the client layer again
from there.
Because of that, we create the extra entry for that new layer when the
client layer compilation finishes in the `finishModules` phase. The new
entry is handled normally as it's in the server layer. But the original
module in the client layer will be compiled specially as special no-op
exports, and will then be connected via the `callServer` wrapper.
fix NEXT-809 ([link](https://linear.app/vercel/issue/NEXT-809)).
4c3f59f88d