runtime.NumGoRoutine lies

[dgryski]

We should fix https://github.com/tinygo-org/tinygo/blob/release/src/runtime/debug.go#L17

[aykevl]

The runtime currently does not track which goroutines exist. So this information is not currently available.

This actually has an interesting benefit: goroutines are just plain old data structures to the garbage collector. If two goroutines are deadlocked with each other for example, they should get garbage collected like any other object on the heap. Because the GC doesn't know these are goroutines, it can't lower a count of goroutines for example.

(This could be fixable in the precise GC, by using special values for the "layout" value).