Allow otel module directives

[puneetsarna]

https://nginx.org/en/docs/ngx_otel_module.html

Proposed changes

Describe the use case and detail of the change. If this PR addresses an issue on GitHub, make sure to include a link to that issue using one of the supported keywords here in this description (not in the title of the PR).

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md)

[ornj]

There are already directives from dynamic modules in crossplane (notably NJS), but the point has been made in the past that perhaps these should be "add ons" rather than included in the core map in analysis.go. I think this has some merit as you could "customize" crossplane to be aware of whatever non-standard modules you are using.

This could allow using crossplane with unknown 3rd party modules or better support those that allow configurations that can look very different from the usual NGINX configs (Lua).

Since there are already directives from "first party" nginx modules in crossplane, I think move forward with reviewing and merging this PR.