Create a sysctl host analyzer

[JGAntunes]

Describe the rationale for the suggested feature.

Related to - #1674.

The current sysctl analyzer is in cluster specifc:

• https://troubleshoot.sh/docs/analyze/sysctl/

• troubleshoot/pkg/analyze/sysctl.go

  Lines 41 to 44 in f0b8de6

  	// The when condition for outcomes in this analyzer is interpreted as "for some node".
  	// For example, "when: net.ipv4.ip_forward = 0" is true if at least one node has IP forwarding
  	// disabled.
  	func (a *AnalyzeSysctl) analyzeSysctl(analyzer *troubleshootv1beta2.SysctlAnalyze, findFiles getChildCollectedFileContents) (*AnalyzeResult, error) {

In our view a sysctl collector for the host, before a cluster is actually running is pretty valuable. Particularly for a lot of the work currently being done in embedded cluster - (e.g. replicatedhq/embedded-cluster#1449 as well as ongoing work for arp filter detection).

Describe the feature

The analyzer spec would basically be the same as the one we have right now for the in cluster one:

(...)
  analyzers:
    - sysctl:
        checkName: IP forwarding enabled
        outcomes:
        - fail:
            when: "net.ipv4.ip_forward = 0"
            message: "IP forwarding is not enabled"

Seems like for the current analyzer we also support greater/lower than comparisons, so it probably makes sense to support that here too:

• https://github.com/replicatedhq/troubleshoot/blob/main/pkg/analyze/sysctl.go#L163-L246

Describe alternatives you've considered

See - #1674 for a list of the alternatives considered

[JGAntunes]

Done in #1681