feat: auto set GOMEMLIMIT when memory is limited

[kruskall]

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

[mergify]

This pull request does not have a backport label. Could you fix it @kruskall? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• backport-8.x is the label to automatically backport to the 8.x branch.

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label.

[marclop]

I missed this in the first review, but isn't a 1 second refresh interval a bit on the aggressive side? I haven't delved into the details of the library, but it seems like a waste of CPU cycles.

[kruskall]

aaah, this was there for testing. It should be 30s like the max procs check 😭

[kruskall]

#14939