update population and GDP data (in US$2005)

[LaviniaBaumstark]

Purpose of this PR

New input data (6.77) including updated GDP (in 2005 $US) and population data and new CES paramter and gdx files for SSP2, SSP2-EU21, SSP1 and SDP_MC. Switch default from SSP2EU to SSP2.
ATTENTION: currently no consistent CES parameter for the new GDP and population data for other scenarios than SSP2, SSP2-EU21, SSP1 and SDP_MC available.

Type of change

• Minor change (default scenarios show only small differences)

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
• 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:
  • calibration runs: /p/tmp/lavinia/MO/test_2005GDPaPOPaSSP2_calibration/remind
  • test runs: /p/tmp/lavinia/MO/test_2005GDPaPOPaSSP2_2024_06_15/remind
• Comparison of results (what changes by this PR?):