Introduce initial conversion webhook for beta version

[a-thaler]

Description

In preparation of applying the beta API changes (#767), a conversion webhook needs to get established as part of the experimental release.

Criterias

• There is a conversion webhook in place which gets called on any beta API LogPipeline queries only
• kubebuilder approach for conversion webhooks is in use
• The webhook uses the same cert mechanism as the existing validation webhook, so that no cert expiry can happen
• The webhook is only active for the experimental release
• Rename and covert the LogPipeline.input.application attribute and add the "enabled" attribute as outlined in LogPipeline Beta API #1395
• Re-use the existing crypto logic for certificate handling

Reasons

Attachments

Release Notes

[skhalash]

The conversion webhook infrastructure has been set up, but its functionality is currently limited—it only renames the application input to runtime. One open question remains: how should we monitor this setup (e.g., alerts, dashboards, etc.)? While controller-runtime offers webhook metrics, which we are already scraping, we need to further define a comprehensive monitoring approach.