splitWorkerEnv(env: Readonly<Record<string, unknown>>): SplitWorkerEnv
Partitions a Workers env record by value type.
Values that are neither a string nor a non-null object (a number, a boolean,
null, undefined) land in neither half: coercing them to a string would
put a value in env that was never a variable, and treating them as a
binding would hand a caller something with no methods.
The string variables and the object bindings, separated