the allowed set of wasm features is not clear
when working on https://github.com/aduros/wasm4/pull/749, i wondered what wasm features are allowed to be used by carts.
however, i couldn't find documentation stating it.

for example, bulk-memory instructions are used by some of carts out there.
otoh, C Makefile provided by w4 doesn't enable it.

i guess it's "whatever wasm3 support"?
