cmd/cgo: add #cgo noescape/nocallback annotations

When passing pointers of Go objects from Go to C, the cgo command generate _Cgo_use(pN) for the unsafe.Pointer type arguments, so that the Go compiler will escape these object to heap.

Since the C function may callback to Go, then the Go stack might grow/shrink, that means the pointers that the C function have will be invalid.

After adding the #cgo noescape annotation for a C function, the cgo command won't generate _Cgo_use(pN), and the Go compiler won't force the object escape to heap.

After adding the #cgo nocallback annotation for a C function, which means the C function won't callback to Go, if it do callback to Go, the Go process will crash.

Fixes #56378

Change-Id: Ifdca070584e0d349c7b12276270e50089e481f7a
GitHub-Last-Rev: f1a17b08b0590eca2670e404bbfedad5461df72f
GitHub-Pull-Request: golang/go#60399
Reviewed-on: https://go-review.googlesource.com/c/go/+/497837
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

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