wasi: fix serdes bugs from snapshot1 migration

During the migration to WASI snapshot1, a field was removed
from the subscription type. The field was removed from the
code, but the bounds checking logic was not updated. This
commit updates that check.

Similarly, __wasi_linkcount_t changed from a uint32_t to a
uint64_t. However, the bounds checks were missed, and the code
was still writing uint32_t's (to the new correct offset) instead
of uint64_t's. This commit updates that logic as well.

Refs: https://github.com/nodejs/node/pull/30980

PR-URL: https://github.com/nodejs/node/pull/31122


Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>