Add attribute.Any() to simplify dynamic attribute construction

[ch0s1n]

Problem Statement

I'm often frustrated when I need to convert dynamic or mixed-type data (e.g. from map[string]interface{} or JSON payloads) into OpenTelemetry attributes. The current API only provides type-specific constructors such as attribute.String(), attribute.Int(), and so on, which requires repetitive and verbose type-switching logic in user code.

This makes it inconvenient to handle arbitrary structured data in a generic way, especially when building spans programmatically from logs, requests, or metadata.

[pellared]

I am against this proposal because of there would be breaking behavioral change if the specification would add new type to https://github.com/open-telemetry/opentelemetry-specification/tree/main/specification/common#attribute (e.g. open-telemetry/opentelemetry-specification#4485)

which requires repetitive and verbose type-switching logic in user code

One can always create a reusable function himself.