defaultLayer in several high-fan-in modules is currently composed at import
time. This makes module evaluation sensitive to transitive import order, even
though the layer graph itself is unchanged.
Wrap these compositions in Layer.suspend() so the same graph is built on
demand instead of during module load. This reduces init-order coupling and
makes import reordering for startup work safer.
I ran into this while trying to improve startup time by moving imports around.
No functional change intended.
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