Support for (near real time) time varying carbon intensity

[freemin7]

As suggested in Nanoseb/gqueue#2 there are power grids where there is a lot of deviation of the carbon intensity hour by hour (15 min by 15 min) over the year. See some of those:

https://app.electricitymaps.com/zone/DE
https://www.nowtricity.com/country/germany/
https://www.climatiq.io/electricity-carbon-emissions
https://www.fingrid.fi/en/electricity-market-information/real-time-co2-emissions-estimate/
https://carbonintensity.org.uk/
https://www.agora-energiewende.de/service/agorameter/chart/power_generation/18.07.2023/21.07.2023/today/
https://www.caiso.com/todaysoutlook/Pages/emissions.html

Both requesting/collecting historic data would be a huge boon in this software suite. Having insight into this could motivate SLURM to create a CO2 intensity aware or electricity price aware scheduling which could make a huge impact.