Update infrastructure for generating conversion files for DECARB scenarios

[trynthink]

Update input data file creation infrastructure to be able to generate the following files:

• emm_region_emmission_prices-DECARB-high.json
• emm_region_emmission_prices-DECARB-mid.json
• emm_region_emmission_prices-DECARB-bau.json
• site_source_co2_conversions-DECARB-high.json
• site_source_co2_conversions-DECARB-mid.json
• site_source_co2_conversions-DECARB-bau.json

[trynthink]

These files are generated using currently untracked infrastructure required because they use custom ReEDS runs conducted for DECARB. The data from these custom runs are similar in format to the Cambium data, but not identical, thus cambium_updater.py was not revised to support the data. We can consider whether or not we want these files and the corresponding configuration options available on master long term.