feat: auto set GOMEMLIMIT when memory is limited (backport #14882)

[mergify]

Motivation/summary

By default memlimit uses all the memory available on the host but if cgroups are used and the process is being limited we want to use the correct max memory.
Use automemlimit lib to set memory limit
Run check every 30s
Similar approach as automaxprocs

Test has to be performed manually (see below) because we can't really restrict the process memory :(

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

• make apm-server
• docker run -it -v ./:/apm-server --memory=4096m golang
• cd /apm-server && ./apm-server -e
• observe the the log line changing the memlimit

Related issues

Closes #14475

---

This is an automatic backport of pull request #14882 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 4940a7e has failed:

On branch mergify/bp/8.x/pr-14882
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 4940a7ea.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   internal/beatcmd/beat.go
	new file:   internal/beatcmd/memlimit.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   NOTICE.txt
	both modified:   go.mod
	both modified:   go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[kruskall]

@Mergifyio queue

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 3cd7dc3