[tsgen] Remove asyncify function exports assertions.

[brendandahl]

When using tsgen with -sASYNCIFY=1 and assertions enabled, an assertion failure occurs: Assertion failed: missing Wasm export: asyncify_start_unwind. This is due to #25541.

This PR disables assertions for the _asyncify_<x> exports when running tsgen to resolve the issue.

Continuation of #25780

[brendandahl]

Looks like some AOT JS tests rely on the assertions being in the code. I'm thinking I'll just disable ASYNCIFY=1 during tsgen.

[sbc100]

Looks like some AOT JS tests rely on the assertions being in the code. I'm thinking I'll just disable ASYNCIFY=1 during tsgen.

Will it no change the possible shape of the API? At least the JS looks different with that option enabled vs disabled.

The other option is to wait until post-asyncify to run the TS bindings generation?

[brendandahl]

Will it no change the possible shape of the API? At least the JS looks different with that option enabled vs disabled.

It will change the API, but we don't currently generate the correct definitions for async exported functions with JSPI or Asyncify. This is something we should probably fix at some point. FWIW, async embind exports have the correct definitions.

The other option is to wait until post-asyncify to run the TS bindings generation?

The issue with waiting until after binaryen is run, is that is also post optimization. After opt, emscript doesn't work with the minified binary.

AFAICT, the only special functions that binaryen adds are the asyncify_<x>. I'm thinking I'll make a special case for those in the assertions when running with tsgenertion. That way I don't have to disable assertions or asyncify.