Aggregation intervals should be an exact match

[tomkerkhove]

Aggregation intervals should be an exact match instead of determining the closest aggregation interval that is available.

We are changing this give it can result in odd metrics. Imagine you've configured it to use intervals of 10 minutes, but it only supports 1h, it will implicitly use 1h without the consumer knowing.

This required #464 to be implemented first.

[tomkerkhove]

Relates to https://github.com/tomkerkhove/promitor/issues/570 Relates to https://github.com/tomkerkhove/promitor/issues/791