cmd/link: on wasm, number of functions limited to 2^16 [1.24 backport]

[cherrymui]

Manually creating a backport issue for #64856 as there were previously closed backport issues (#64868).

This causes build failure or runtime failure for large Wasm programs, and there is no workaround. Thanks.

[cherrymui]

Let's wait for a month after 1.25 is out.

[Jorropo]

Anything changed between #64868 and now that would make this arguments no longer apply ?

[cherrymui]

This issue is a backport request, for discussion. As you see, it is not yet approved.

One part is that we re-evaluated the risk of the code change. Despite the code being tricky, if anything goes wrong, it will fail hard, either as a build failure or very early at runtime execution. So it is not as risky as I initially thought.

That said, not to backport is still a reasonable outcome of this issue.