Effect tracking with recursive functions and extra effect incorrectly depends on call order

[stephanemagnenat]

The following code:

fn b(f) {
    a(f, || effects::write())
}

fn a(f, g) {
    b(f); f(); g(); ()
}

(where effects::write() is a nop function with write effects (see effects test module).

Has incorrect effect type schema for a:

fn a (() → A ! e₀, () → B) → () ! e₀, Write

Where it should be:

fn a (() → A ! e₀, () → B ! e₁) → () ! e₀, e₁, Write