Decouple Audit logging from the AntreaPolicy feature gate

[antoninbas]

Not introduced by the PR, but shouldn't loggingEnabled always be true given logging can be enabled for K8s NetworkPolicy? @qiyueyao
If yes, we should make the struct name of AntreaPolicyLoggerOptions not specific to AntreaPolicy?

Originally posted by @tnqn in #5337 (comment)

At the moment, Audit logging is only enabled when the AntreaPolicy feature gate is enabled (which is the default):

antrea/cmd/antrea-agent/agent.go

Lines 430 to 442 in 5255b20

	// In Antrea agent, status manager and audit logging will automatically be enabled
	// if AntreaPolicy feature is enabled.
	statusManagerEnabled := antreaPolicyEnabled
	loggingEnabled := antreaPolicyEnabled
	var auditLoggerOptions *networkpolicy.AntreaPolicyLoggerOptions
	if loggingEnabled {
	auditLoggerOptions = &networkpolicy.AntreaPolicyLoggerOptions{
	MaxSize: int(o.config.AuditLogging.MaxSize),
	MaxBackups: int(*o.config.AuditLogging.MaxBackups),
	MaxAge: int(*o.config.AuditLogging.MaxAge),
	Compress: *o.config.AuditLogging.Compress,
	}
	}

However, Audit logging can also be enabled for K8s NetworkPolicies (by annotating the Namespace in which the NPs are defined with an Antrea-specific annotation). So it should be possible for someone to leverage Audit logging for K8s NPs even when disabling the AntreaPolicy feature.

The naming of objects in pkg/agent/controller/networkpolicy/audit_logging.go could also be more generic, to avoid tying it to the AntreaPolicy feature.