Allow Prometheus exporter to add resource attributes to metric attributes

[asafm]

Fixes #3705

Changes

Allowing exporters (e.g. Prometheus exporter) to add the resource attributes to each exported metric attributes

• Related issues Prometheus Exporter: Copy Resource attributes into each time-series attributes #3705
• CHANGELOG.md file updated for non-trivial changes
• spec-compliance-matrix.md updated if necessary

[asafm]

@dashpole I wasn't sure what to do with changelog and matrix

[asafm]

@dashpole What should I do with changelog and matrix?

[dashpole]

I don't think this needs to be in the matrix. You can add to the changelog under Unreleased > Metrics something like "- add optional configuration for prometheus exporters to promote resource labels to metric labels (#3761)"

[asafm]

@dashpole Updated changelog

[asafm]

@MrAlias Can you take another look?

[MrAlias]

Please be sure to update the PR title.

[arminru]

You might want to look at @pirgeo's proposal about how conflicts encountered while flattening are to be handled: #2736

[asafm]

@cijothomas Can I resolve the conversation?

[asafm]

@cijothomas Who else is needed to approve?

[cijothomas]

@cijothomas Who else is needed to approve?

I am not an owner to merge this, but I think its best to get another round of review from @jack-berg and @arminru who reviewed this PR earlier!

[jack-berg]

Small recommendations I think would improve the readability but content looks good.

[asafm]

@jack-berg Ready to merge 🎉

[asafm]

@carlosalberto @dashpole Ready to merge