make Prometheus evaluation intervals configurable

[Horiodino]

Component(s)

collector, target allocator

Describe the issue you're reporting

Description
The allocator currently uses hardcoded EvaluationInterval values when generating the Prometheus CR. These should be configurable through PrometheusCRConfig so users can override them if needed.

Proposed Change
Use values from PrometheusCRConfig when provided, otherwise fallback to Prometheus Operator defaults .

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