Embodied Emissions: consider making estimate of all the embodied emissions optional

[dschien]

Data on all aspects is very sparse, in particular on "Total Embodied Emissions" and "Expected Lifespan", notwithstanding the methodological ambiguity mentioned in issue https://github.com/Green-Software-Foundation/software_carbon_intensity/issues/152

The potential to develop a concrete method based on this standard will be limited by this requirement.

[atg-abhishek]

Can you clarify more on what you mean by data is very sparse? The standard cannot be too prescriptive tying it down to specifics cc @jawache @Henry-WattTime