Change the workflow on how we set the right permissions for perf-plugin

[tkatsoulas]

Summary

The current workflow has a flaw, the post installation script tries to set capabilities without making sure that the system supports them, so the script fails.

The new workflow follows the least privileged approach. Uses the CAP_PERFMON in systems that support it and if it fails to set CAP_SYS_ADMIN then sets the setuid bit.

Test Plan

On a deb based environment without support for CAPS

1. Build native packages locally for your arch https://github.com/netdata/netdata/blob/master/packaging/building-native-packages-locally.md
2. Install them.
   installation must finish without errors
3. dpkg --configure -a, must not return any errors.

Closes #16556

[tkatsoulas]

I will spin up test envs for the 3 cases

• with cap_perfmon
• without cap_perfmon but supporting capabilities
• without capabilities support

[ilyam8]

@tkatsoulas I think it looks good now and will work. A minor note: we don't echo "Set..." in other postint files, i don't know if that is good practice or not to echo something in those files cc @Ferroin If not and you add echo to not have first branch empty, consider the following:

if ! first && ! second; then
  action
fi

if that is not a big deal nvm, lgtm.

[Ferroin]

@tkatsoulas I think it looks good now and will work. A minor note: we don't echo "Set..." in other postint files, i don't know if that is good practice or not to echo something in those files cc @Ferroin If not and you add echo to not have first branch empty, consider the following:

if ! first && ! second; then
  action
fi

if that is not a big deal nvm, lgtm.

It’s generally not recommended to echo stuff there, but it’s not a major issue in most cases either.