fix: use only aggregation set labels for MWMBR expressions

fix: use only aggregation set labels for MWMBR expressions

This makes sure that we only select for the labels that are present on the aggregation set. In theory, these should be the only labels present on the ratios. But in https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/team/-/issues/6378#note_2136974528 we saw that there was an upscale_source label present that prevented us from joining the 5m and the 1h ratios.

This makes sure this doesn't happen again even if we add labels to one of the ratios but not the other.

fix: remove the upscale_source label from aggregation sets

This removes the upscale_source label from aggregation sets' rate metrics.

It also removes the conditional upscaling of aggregation set transformations in case the direct expression is not possible. This would happen if we want to add a 6h window to an aggregation set, but the source aggregation itself does not have it. We did this because in the Prometheus world of GitLab.com, some of the prometheus-local aggregations did not have the 6h burn rate, we'd only get those in the Thanos aggregations.

We don't need this anymore. For GitLab.com we use upscaleLongerBurnrates to upscale aggregation sets. In that case they're using their own 1h rate for upscaling.

For dedicated, we don't need to worry about this, all aggregation sets have the 6h burn rate. For the component metrics, from source, we're using the source metrics. For the transformation from component to service metrics, the required burnRate is present so no need to upscale.

For https://gitlab.com/gitlab-com/gl-infra/gitlab-dedicated/team/-/issues/6378