test: verify heap buffer allocations occur

Check that small typed arrays, including `Buffer`s (unless allocated
by `Buffer.allocUnsafe()`), are indeed heap-allocated.

PR-URL: https://github.com/nodejs/node/pull/26301


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>