Support OTEL_ATTRIBUTE_COUNT_LIMIT

[owais]

Spec mentions global OTEL_ATTRIBUTE_COUNT_LIMIT env var. According tot he spec, any model specific attribute count limit such as span, event or link attribute count limit should fallback to this if the model specific limit is not specified by the user.

[lzchen]

Perhaps this should be understood as: Even if model specific limit has a default value, if the model specific value is not provided, but OTEL_ATTRIBUTE_COUNT_LIMIT IS provided, it would use the provided global value?

[owais]

That is how I think it should work as well but spec says if the default is provided then it should use the default instead of the global (OTEL_ATTRIBUTE_COUNT_LIMIT).

From the spec:

An SDK MAY implement model-specific limits, for example SpanAttributeCountLimit. If both a general and a model-specific limit are implemented, then the SDK MUST first attempt to use the model-specific limit, if it isn't set and doesn't have a default, then the SDK MUST attempt to use the general limit.

[owais]

I created this issue to clarify or update spec: open-telemetry/opentelemetry-specification#1878