Efp

[FelicitasBeier]

🐦 Description of this PR 🐦

• This PR flexibilizes the selection of the start year and target year of the fading in of the Environmental Flow Policy
• Previously, it faded in "linearly" through the file f42_env_flow_policy.csv and alternative scenarios (e.g. the India country case studies used extra files to set different start and target years (f42_env_flow_policy_india.csv))
• Now the start and target year can be set through s42_efp_startyear and s42_efp_targetyear. The policy then fades in truly linearly using a macro

🔧 Checklist for PR creator 🔧

• Label pull request from the label list.

  • Medium risk: Uncritical changes in the model core (e.g. moderate modifications in non-default realizations)
  • Fading is now linear (before it was nearly linear), minor changes as can be seen in the results shown below

• Self-review own code

  • No hard coded numbers and cluster/country/region names.
  • The new code doesn't contain declared but unused parameters or variables.
  • magpie4 R library has been updated accordingly and backwards compatible where necessary.
  • scenario_config.csv has been updated accordingly (important if default.cfg has been updated)

• Document changes

  • Add changes to CHANGELOG.md
  • Where relevant, put In-code documentation comments
  • Properly address updates in interfaces in the module documentations
  • run goxygen::goxygen() and verify the modified code is properly documented

• Perform test runs

  • Medium risk:
    • Run test runs via Rscript start.R --> "test runs"

📉 Performance changes 📈

• Current develop branch default : 0.3666597
• This PR's default : 0.38881999

Slightly better runtime

Some results:
Tau unchanged

Area actually irrigated

Withdrawal comparing EFP off with EFP on (old and new)

Withdrawal with example of different start and end year compared to previous default

🚨 Checklist for reviewer 🚨

• PR is labeled correctly
• Code changes look reasonable
  • No hard coded numbers and cluster/country/region names.
  • No unnecessary increase in module interfaces
  • model behavior/performance is satisfactory.
• Changes are properly documented
  • CHANGELOG is updated correctly
  • Updates in interfaces have been properly addressed in the module documentations
  • In-code documentation looks appropriate