What does this PR do?

Adds opampextension as a Core component to the EDOT Collector (internal/edot).

Changes:

• Added github.com/open-telemetry/opentelemetry-collector-contrib/extension/opampextension v0.145.0 as a direct dependency in go.mod
• Registered opampextension.NewFactory() in the EDOT Collector's extension factory list (otelcol/components.go)
• Marked opampextension as a Core component in components.yml
• Updated golden files (components-output.yml and components-output-fips.yml) to include the opamp extension entry (stability: Alpha)
• Updated go.sum and NOTICE.txt/NOTICE-fips.txt via go mod tidy and mage notice

Why is it important?

The OpAMP (Open Agent Management Protocol) extension enables the EDOT Collector to communicate with an OpAMP server for remote management and configuration. This will allow Fleet Server to monitor and manage EDOT Collector via OpAMP.

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

No disruptive impact. This adds a new optional extension to the EDOT Collector; existing configurations are unaffected.

How to test this PR locally

Run the EDOT Collector and verify the opamp extension is listed:

elastic-agent otel components | grep opamp

Related issues

Questions to ask yourself

• How are we going to support this in production? The opampextension is an upstream OTel Contrib component maintained by the OTel community.
• How are we going to measure its adoption? Via configuration usage telemetry.
• How are we going to debug this? Standard OTel Collector logging applies; the extension exposes its own status via the health check mechanism.