[8.x](backport #6627) Add redis and nginx otel receivers

[mergify]

What does this PR do?

This PR adds the redis and nginx opentelemetry receiver components to EDOT.

Why is it important?

These 2 receivers will provide support for metrics collection from NGINX and Redis workloads.

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

How to test this PR locally

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #6627 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 300d88e has failed:

On branch mergify/bp/8.x/pr-6627
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 300d88e3e.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   NOTICE.txt
	new file:   changelog/fragments/1738160406-add_redis_nginx_otel_comps.yaml
	modified:   go.mod
	modified:   go.sum
	modified:   internal/pkg/otel/components.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   internal/pkg/otel/README.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[mergify]

This pull request has not been merged yet. Could you please review and merge it @ChrsMark? 🙏