Implement instrument advisory (hint) for Metric API

[cijothomas]

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument-advisory-parameters New spec. The advisory needs to be exposed on Metric API, and then the SDK must leverage them for aggregation.

[cijothomas]

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument-advisory-parameter-explicitbucketboundaries This part is already stable, and I plan to add it soon.

[alfiejfs]

Hi, is this still planned for the beta release on August 2nd? I see it mentioned in #1719 but I don't see it in the milestone. And is this just a temporary API patch whilst views are removed, or is it intended to stay? Cheers :)

[cijothomas]

Hi, is this still planned for the beta release on August 2nd? I see it mentioned in #1719 but I don't see it in the milestone. And is this just a temporary API patch whilst views are removed, or is it intended to stay? Cheers :)

Yes. (Note we got delay by few weeks).
Will fix milestone, thanks for catching it. It'll be a permanent feature, as it is part of OTel's Stable specification.