[OTel Mapper] Fails to convert nested arrays and slices to `[]any`

[pickypg]

Prior to shipping Beat events to OTel via the otelconsumer, Beats attempts to sanitize the mapstr.M map for the pdata library used by OTel.

The sanitization does a few key things, but it serves two wide-reaching purposes:

1. Convert mapstr.M to map[string]any in place.
   • pdata inherently does not know about mapstr.M
2. Convert arrays and slices (including []mapstr.M) to []any.
   • pdata choose to not work with other types.

However, with both purposes, there are two issues:

1. It recursively handles mapstr.M, but it does not recursively handle map[string]any. Any nested slices / arrays within a map[string]any will inevitably fail to be handled by pdata unless they happen to already be []any slices. And, in the unlikely event of a mapstr.M containing a map[string]any containing a mapstr.M, the inner mapstr.M would not be converted.
2. It does not actually convert arrays because it only uses the switch to detect slices.

[elasticmachine]

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