[BUG] Improve usage and code flow of Heuristics + Filtering

[parthosa]

Currently, it seems unclear what should be a Heuristic and what should be a TC Filter. Stating the purpose here. We should also add this in Docs.

Purpose:

• Heuristics: Based on certain metrics, all apps that do not meet the criteria should be downgraded to Not Recommended
  • E.g. Spill Metrics
• Top Candidate Filter: Based on certain metrics, all Recommended apps that do not meet the criteria should not be displayed on console.
  • E.g. Total Core Seconds

The problem is with the usage of unsupported operators. I find the its usage at a very odd place. I think we should move it to Heuristics module.

cc: @amahussein