Improve metadata for benchmarks

[danielelerede-oet]

As discussed with @odow , I'm opening this issue to discuss about the improvement of metadata for the benchmarks on the platform as from https://github.com/open-energy-transition/solver-benchmark/tree/main/benchmarks/jump_highs_platform .
It would be great to have a feedback on some categorizations concerning the distinction between "Operational" and "Optimal power flow models" and the features making some problems MILPs (e.g. the README for PowerModels benchmarks mentions Optimal Transmission Switching but it's not clear which are the problems envisaging that).

[odow]

We can add and maintain the metadata files in this repo if it is best.

Why do we need to specify the sizes? Can't you automatically compute this?
https://github.com/open-energy-transition/solver-benchmark/blob/857f954b0ee57d01adb6db1ff09e870c292f3dbc/benchmarks/jump_highs_platform/Metadata_genx.yaml#L177-L180

[danielelerede-oet]

Hi @odow, your proposal works well for me.
Concerning sizes we can automatically compute them. The points requiring special attention are:

• Kind of problem: Infrastructure/Operational/Optimal power flow (if we want to have a distinction between operational and OPF problems)
• Time horizon: Single stage/Multi-stage
• Temporal resolution: n. of time slices
• Spatial resolution: n. of nodes
• MILP features: