--min-time interferes with pushdown on sidecar

[GiedriusS]

Noticed a small problem with pushdown and --min-time. Since those flags modify the min/max time of a query it means that the data points will fall on different timestamps. With a big enough step parameter it might just happen that even the lookback delta will not be enough - the upper PromQL engine will not "see" those data points and show no data.

Thus, we probably won't be able to support exact --min-time values because the start/end times need to be aligned to the original min/max time and the step parameter.

This actually also applies to when Sidecar uploads a block and the minimum timestamp becomes a fixed value.

[tend2infinity]

Hey, I would like to work on this issue, can I get some guidance regarding how to proceed, Thank you!

[GiedriusS]

Actually, this also applies to when Sidecar uploads a block and the minimum timestamp becomes a fixed value. Sorry, this was a bit of a harder problem that we wanted to fix ourselves so I went ahead and did it: #5142.