sdk: Implement deduplication for MAP

[pellared]

Blocked by:

• attribute: Add MAP type #7935

We have to comply with spec https://opentelemetry.io/docs/specs/otel/common/#mapstring-anyvalue:

The implementation MUST by default enforce that the exported maps contain only unique keys. The enforcement of uniqueness may be performed in a variety of ways as it best fits the limitations of the particular implementation (e.g. by removing duplicates).

[mehrdadbn9]

Hi, I'd like to work on implementing deduplication for the Metrics Aggregation Pipeline (MAP). This is a feature to prevent duplicate metric exports. Could a maintainer please assign it to me? Thank you!