feat(prometheus): expose query method for PromQL queries (#6475)

[bayandzm]

/claim #6475

Description

This PR exposes the existing method as a public method to allow executing arbitrary PromQL queries against the Prometheus server.

Changes

• Rename to (public method)
• Add proper docstring with examples
• Add type hints for better IDE support

Usage

from keep.providers.prometheus_provider.prometheus_provider import PrometheusProvider

provider = PrometheusProvider(...)
result = provider.query("up{job='prometheus'}")
print(result['data']['result'])

This resolves issue #6475 - users can now query Prometheus directly for analysis by AI agents.

This PR was created with AI assistance.

Closes #6475

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