all: change //go:export to //export

This is the kind that is used in Go (actually CGo) for exporting
functions. I think it's best to use //export instead of our custom
//go:export pragma, for consistency (they are equivalent in TinyGo).
Therefore I've updated all instances to the standard format (except for
two that are updated in https://github.com/tinygo-org/tinygo/pull/1024).

No smoke tests changed (when comparing the output hash), except for some
wasm tests that include DWARF debug info and tend to be flaky anyway.

src/internal/task/task_coroutine.go

@@ -10,12 +10,12 @@ import (
 // This matches *i8 in LLVM.
 type rawState uint8
 
-//go:export llvm.coro.resume
+//export llvm.coro.resume
 func (s *rawState) resume()
 
 type state struct{ *rawState }
 
-//go:export llvm.coro.noop
+//export llvm.coro.noop
 func noopState() *rawState
 
 // Resume the task until it pauses or completes.