Support JS symbols that are aliases of native ones

[sbc100]

We can then use this mechanism to replace the hacky way to we map things like memory -> wasmMemory and __indirect_function_table => wasmTable.

[dschuff]

What happens if we ever want to try to remove the leading underscore from native functions? Will this start causing clashes?

[sbc100]

What happens if we ever want to try to remove the leading underscore from native functions? Will this start causing clashes?

I don't think it makes the situation WRT removing underscores any worse. Already if you declare $foo as a JS library function it would be called foo in the generated code which would conflict with the native foo if were were not prefix the native one with an underscore.

[dschuff]

It looks OK? TBH I'm not sure I really understand the JS linking system deeply enough to know whether this is really a good idea though.

[sbc100]

This idea is that this allows us to have JS names that don't match the native symbol names.

In particular this simplifies the memory and table export handling. I think this is needed for my ongoing work on dynamic linking, but it actually might not me. I can can hold off landing this and circle back parhaps if it proves truely necessary.

[dschuff]

If this is really an improvement on its own, then I think it's fine to add it. I just don't have a high confidence in my review.