make cement process emissions variable for conopt

[JakobBD]

Purpose of this PR

So far, cement process emissions were fixed to a value based on the previous iteration's ue_cement.
ue_cement therefore only saw energy-related emissions as an incentive for reduction.

This PR makes cement process emissions a function of ue_cement in the current iteration, such that CONOPT sees the incentive to reduce ue_cement.

I still have to check and clean up the fixing of vm_macBase and vm_emiIndBase in core/presolve.gms, as process cement CCS cost enters the budget equation twice right now.

TBD if we like the results, and if we want to do some ad-hoc adaptation, e.g. to CES elasticities.

Type of change

(Make sure to delete from the Type-of-change list the items not relevant to your PR)

• Bug fix
• Refactoring
• New feature
• Minor change (default scenarios show only small differences)
• Fundamental change
• This change requires a documentation update

Checklist:

• My code follows the coding etiquette
• I performed a self-review of my own code
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted the reporting in remind2 where it was needed
• I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• All automated model tests pass (FAIL 0 in the output of make test)
• The changelog CHANGELOG.md has been updated correctly

Further information (optional):

• Test runs are here: /p/tmp/jakobdu/remind_temp2
• Comparison of results (what changes by this PR?):

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

I tested this too, same result (unsurprisingly).

Weird to see these differences between AMT and stock develop runs, though.
I do not see any point in adjusting CES elasticities over this.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

In general I would split this in two: the small change of moving vm_emiIndBase("co2cement_process") from presolve into an equation, that has a lot of impact on model behaviour, and the large code shuffling involving fixed_shares, that has no influence on model behaviour at all.

[JakobBD]

Doing final tests on this after separating the fixed_shares refactoring (same directory as above, newest two runs).
From my side ready to merge once these tests have passed.

[JakobBD]

Tests came back fine, ready to merge from my point of view.