Update Installation.md to replace all plugin-specific examples.

[iagusev]

Description

This PR updates the installation documentation to replace all plugin-specific examples (such as calico and nginx-ingress-controller) with a neutral example-plugin.

The goal is to make the documentation more generic and easier to follow for users implementing their own plugins, without being tied to any specific one.

Fixes # (issue)

Solution

• Replaced calico and nginx-ingress-controller with example-plugin in all YAML examples in documentation/Installation.md.
• Updated paths, pod names, DaemonSets, Deployments, and CLI commands to match the neutral plugin name.
• Preserved all structure and parameters (timeout, retries, destination_groups, apply_required, etc.) from the original examples.
• Ensured consistency across all examples so they now reflect a generic, reusable pattern for plugin installation procedures.

Checklist

• I have commented my code, particularly in hard-to-understand areas (documentation edits explained)
• I have made corresponding changes to the documentation
• There is no breaking changes, or migration patch is provided
• Integration CI passed
• Unit tests. Not applicable for documentation-only change
• There is no merge conflicts

Unit tests

Not applicable, this change only updates documentation examples.

[github-actions]

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