Handle MemoryFill and MemoryCopy operators

[andreiltd]

I found I needed this to weval spidermonkey using latest stable release 147_0_4 and wasi-sdk@30.

[cfallin]

Thanks!

[cfallin]

Separately, you'll probably want to add emission for these operators in the backend (src/backend/mod.rs, lower_op).

[andreiltd]

Separately, you'll probably want to add emission for these operators in the backend (src/backend/mod.rs, lower_op).

It looks like these are already handled in the backend? See: https://github.com/bytecodealliance/waffle/blob/main/src/backend/mod.rs#L563C1-L571C14

[cfallin]

Ah, great; I can't claim to remember all code I've written I guess :-) Thanks, and sorry for missing the frontend half!