Add support for FreeVarReference::Error (#6177)
### Description
Next.js needs a way to error when certain globals are used in the edge
runtime. For example `setImmediate`, to cause an error at compile time.
This implements support for `FreeVarReference::Error` which can be used
to provide an error message.
Since the internals already track the span the message is applied with
the right code location automatically.
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