Add Kubernetes / container runtime information to heartbeat command control logic

[artursarlo]

This PR aims to:

• Add Kubernetes / container runtime information to GProfiler backend using the heartbeart command control logic;

Description

To support this feature:

• The agent has been modified to send "k8s" / "container runtime" information through the POST /metrics/heartbeat endpoint;
• Now the backend is being modified to process this information and persist it on DB;

Related Issue

N/A

Motivation and Context

This PR is a first step towards enabling profiling at:

• Container level;
• Pod level;
• Namespace level;
  For now this only populates the DB with container runtime information for each connected host.

How Has This Been Tested?

Locally:

• Performing direct calls to the POST /metrics/heartbeat endpoint;
• Connecting a compatible agent to the local backend service;

Screenshots

N/A

Checklist:

• I have updated the relevant documentation.
• I have added tests for new logic.