internal/abi: implement initial version of this package

This package can never be a full version as seen in upstream Go, because
TinyGo is very different. But it is necessary to define so that no code
can accidentally use this package (now or in the future).

It currently defines:

  - NoEscape which is needed by strings.Builder since Go 1.23.
  - FuncPCABI* which is needed by internal/syscall/unix on MacOS.

loader/goroot.go

@@ -236,6 +236,7 @@ func pathsToOverride(goMinor int, needsSyscallPackage bool) map[string]bool {
 		"device/":               false,
 		"examples/":             false,
 		"internal/":             true,
+		"internal/abi/":         false,
 		"internal/binary/":      false,
 		"internal/bytealg/":     false,
 		"internal/cm/":          false,