[FEATURE] host pid mode support for k3s-server and k3s-agent

[hlts2]

What

To support eBPF profile, I added an option to support host pid mode for k3s-agent and k3s-server.

The following is an example of usage.

k3d cluster create --host-pid-mode=true

Why

In order to enable eBPF in docker environment, the option pid=host is required.

I deployed the manifest(pyroscope) to a k3d cluster, but could not get the eBPF event properly because k3s-server and k3s-agent docker container were not started in host pid mode.

With this PR fix, k3s-server and k3s-agent will be started in host pid mode, so eBPF will be available in the k3d environment.

[hlts2]

The test seems to be failing, but when I executed make e2e on the main branch, I got the same error...:sob:

Try #15: 'kubectl exec testimage -- ping -c1 host.k3d.internal'
ping: bad address 'host.k3d.internal'
command terminated with exit code 1
Command 'ping -c1 host.k3d.internal' in pod 'testimage' did NOT return successfully in 15 tries
2022-01-17 08:54:46 UTC [Test | lifecycle | ] >>> Pinging host.k3d.internal failed
2022-01-17 08:54:46 UTC [Test | lifecycle | ] >>> FATAL: test failed
2022-01-17 08:56:30 UTC [Runner] >>> FINISHED BASIC TESTS
  > Total:	12
  > Run:	12
  > Skipped:	0
  > Passed:	11
  > Failed:	1

cc: @iwilltry42

[iwilltry42]

Hi @hlts2, thanks for your contribution! :)
Looks simple and good. I just have one comment about structuring the config, as I think this option belongs to the runtime options.

[iwilltry42]

LGTM!

[iwilltry42]

Tests are passing for me (actually I can't get them to fail like they do in CI, but that's unrelated to this PR anyway).
Note: I may need to refactor this into v1alpha4 config version later, but it won't alter the functionality.

Thank you!