eBPF different improvements

[thiagoftsm]

Summary

Fixes #13626

This PR is fixing the following issues:

• Improve PID monitoring;
• Remove errors when plugin runs on CentOS 7.9, because there was not tracepoint available for OOMkill to run there.
• Fix count in netdata.ebpf_threads chart when legacy code is used.

and it also brings less CPU/Memory usage and libbpf 1.0.

Test Plan

1. Compile this branch and start netdata.
2. Wait few seconds to process runs and check that :

• You are not having libbpf warnings: grep libbpf /var/log/netdata/error.log
• Take a look at chart apps.cpu and verify that ebpf.plugin is lower or equal apps.plugin.
• If you have bpftool installed, you can run bpftool map show | grep 10922 and verify that PID tables are not having more the default size 32768, if you do not have take a look in the table present at Additional information.
• If you have a CentOS 7.9 VM, compile this branch and take a look that you won't have the OOMkill thread started, instead you will have the following warning:

2022-09-07 12:29:04: ebpf.plugin INFO  : EBPF OOMKILL : Disabling OOMKILL thread, because kernel does not have necessary tracepoints.
2022-09-07 12:29:05: ebpf.plugin INFO  : EBPF OOMKILL : thread with task id 1956 finished

Additional Information

This PR was tested on:

Linux Distribution	kernel version	BPFTOOL	CPU chart	Threads chart
Slackware Current CO-RE	5.19.6	slackware_5_19_bpftool.txt	slackware_5_19_cpu.txt	slackware_5_19_threads.txt
Slackware Current Legacy	5.19.6	slackware_5_19_legacy_bpftool.txt	slackware_5_19_legacy_cpu.txt	slackware_5_19_legacy_threads.txt
Ubuntu 22.04	5.15.0-33-generic	ubuntu_5_15_bpftool.txt	ubuntu_5_15_cpu.txt	ubuntu_5_15_threads.txt
Alma 9	5.14.0-70.17.1.el9_0.x86_64	---	alma_5_14_cpu.txt	alma_5_14_threads.txt
Debian 11	5.10.0-16-amd64	debian_5_10_bpftool.txt	debian_5_10_cpu.txt	debian_5_10_threads.txt
Slackware Current	5.4.210	slackware_5_4_legacy_bpftool.txt	slackware_5_4_legacy_cpu.txt	slackware_5_4_legacy_threads.txt
Alma 8.6	4.18.0-372.19.1.el8_6	alma_4_18_bpftool.txt	alma_4_18_cpu.txt	alma_4_18_threads.txt
Ubuntu 18.04	4.15.0-180	ubuntu_4_15_bpftool.txt	ubuntu_4_15_cpu.txt	ubuntu_4_15_threads.txt
CentOS 7.9	3.10.0-1160.71.1.el7.x86_64.	centos_3_10_bpftool.txt	centos_3_10_cpu.txt	centos_3_10_threads.txt

For users: How does this change affect me?

Describe the PR affects users: - Which area of Netdata is affected by the change? ebpf.plugin - Can they see the change or is it an under the hood? If they can see it, where? Yes, they can use `apps.cpu` to verify that plugin is using less resource. - How is the user impacted by the change? A plugin more stable and faster. - What are there any benefits of the change? A better plugin

[vlvkobal]

Fixes #13626

Fixes or probably fixes?

[thiagoftsm]

Fixes #13626

Fixes or probably fixes?

Fixes, the tests are showing that ebpf.plugin is always using less resources than apps.