[9.0](backport #45008) [OTel] Support Serializing nested data

[mergify]

This adds support for map[string]any and also arrays in general (as opposed to just slices) to the converted map.

Like mapstr.M and []mapstr.M, this will dive into the map[string]any and []map[string]any objects to ensure that they are properly converted for the pdata code.

Proposed commit message

Properly handles nested map[string]any and array types (not just slices) for OTel conversion to avoid Invalid type warnings from OTel.

Checklist

• 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.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

This should make the code more flexible -- not less.

Author's Checklist

• Ensure nested types are serialized.

How to test this PR locally

The easiest way is to inspect the new test and try removing the updated code to see what changes.

Related issues

• Closes [OTel Mapper] Fails to convert nested arrays and slices to []any #45007

Use cases

Metricsets can now ship nested map[string]any that contain arrays and slices, including of []map[string]any.

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This is an automatic backport of pull request #45008 done by Mergify.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)