Add vulnerabilities risk score finder

What does this MR do and why?

1. Adds risk score aggregation query to Search::Elastic::VulnerabilityAggregations
2. Uses the above query in Search::Elastic::VulnerabilityQueryBuilder
3. Creates Security::VulnerabilityElasticRiskScoresFinder which uses the above query to fetch project/group risk scores.

Logic -

Project/Group Risk Score = min(1.0, (ΣVulnerability_risk_score + (ΣVulnerability_age_in_month) x 0.005) × 1/√(number_of_vulnerabilities))

Keeping that in mind if we look at the score formula closely vulnerability_age_in_months is nothing but -

Σ(current_time - created_at) which can be simplified further to

Num_vulnerabilities*current_epoch_time - Σcreated_at_in_epoch_time

We can then use this simplification to calculate total risk scores without using scripts. More info on the issue - #571079 (comment 2816510162)

References

Relates to - #571079

Screenshots or screen recordings

Before	After

How to set up and validate locally

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