[FEATURE] Migrate gas related TYNDP 2020 to 2024

[CarlosEpia]

Complete TYNDP 2024 migration: gas sector

Follow-up to #1443. The electricity-side migration (electrical_neighbours.py, tyndp.py) is done and verified in production. The gas sector (gas_neighbours/eGon2035.py) still runs on TYNDP 2020 data. This was kept intentionally working via a legacy download (capacities_2020_gas_legacy in tyndp.py) so it wouldn't break in the meantime.

Remaining work

• Rewrite calc_capacities() (gas production capacities) for the TYNDP 2024 wide-table format
• Rewrite calc_global_ch4_demand()
• Rewrite calc_global_power_to_h2_demand()
• Rewrite calculate_ocgt_capacities()
• Build a gas-side map_carriers_tyndp() equivalent. Needs inspecting TYNDP 2024's H2/CH4 output files (MMStandardOutputFile_*_H2_v11_SoS.xlsb), not yet done
• Update gas_neighbours/__init__.py source config to the new 2024 files
• Remove the capacities_2020_gas_legacy download in tyndp.py once gas no longer needs it
• Update sanity_checks.py's etrago_eGon2035_gas_abroad(), which imports gas's capacity functions directly

Note: the remaining work could include more items that I did not see while creating this issue