Change forEach to forEachLimit when emitting assets

[sokra]

cherry-picked from #8609

What kind of change does this PR introduce?
memory usage improvement

Did you add tests for your changes?
N/A

Does this PR introduce a breaking change?
no

What needs to be documented once your changes are merged?
nothing

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[webpack-bot]

For maintainers only:

• This need to be documented (issue in webpack/webpack.js.org will be filed when merged)

[dav-is]

This change doesn't improve memory usage. It only delays the allocation. The memory is never freed. With this change alone, our process still runs out of memory.

[sokra]

This change doesn't improve memory usage. It only delays the allocation. The memory is never freed.

It improves memory usage a bit, because only 15 buffers allocated here are used at the same time.

I know that it's not free. I'll comment on the other PR.

[axetroy]

If you change the forEach elsewhere to forEachLimit, can we improve memory usage?

Because the latest version of webpack still has problems with excessive memory.