n-api: defer Buffer finalizer with SetImmediate

src: fix off-by-one error in native SetImmediate

Previously, the throwing callback would have been re-executed in case of an exception. This patch corrects the calculation to exclude the callback.

n-api: defer Buffer finalizer with SetImmediate

We have a test that verifies that JS execution from the Buffer finalizer is accepted, and that errors thrown are passed down synchronously.

However, since the finalizer executes during GC, this is behaviour is fundamentally invalid and, for good reasons, disallowed by the JS engine. This leaves us with the options of either finding a way to allow JS execution from the callback, or explicitly forbidding it on the N-API side as well.

This commit implements the former option, since it is the more backwards-compatible one, in the sense that the current situation sometimes appears to work as well and we should not break that behaviour if we don’t have to, but rather try to actually make it work reliably.

Since GC timing is largely unobservable anyway, this commit moves the callback into a SetImmediate(), as we do elsewhere in the code, and a second pass callback is not an easily implemented option, as the API is supposed to wrap around Node’s Buffer API. In this case, exceptions are handled like other uncaught exceptions.

Two tests have to be adjusted to account for the timing difference. This is unfortunate, but unavoidable if we want to conform to the JS engine API contract and keep all tests.

Fixes: https://github.com/nodejs/node/issues/26754 (as far as the non-build part is concerned)

@nodejs/n-api

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines