build: add python3.14 support

[sbrunato]

Adds python3.14 support (now used in as max supported version in CI).

Adapt tests to cfgrib availability (does not install on windows + python 3.14)

[github-actions]

Benchmark comparison

Compared baseline: origin/develop
Compared candidate: 55e1df6

--------------------------------- benchmark: 5 tests, 2 sources ---------------------------------
Name (time in us)                                     baseline Median  candidate Median   ΔMedian
-------------------------------------------------------------------------------------------------
test_benchmark_eoproduct_instantiation                        32.3860           32.7620     +1.2%
test_benchmark_eoproduct_assets_population                    66.8750           66.7550     -0.2%
test_benchmark_import_eodag_cube_subprocess               14,978.1910       14,939.2715     -0.3%
test_benchmark_to_xarray_local                            16,800.3920       17,608.2620     +4.8%
test_benchmark_import_eodag_public_api_subprocess        699,630.9040      701,122.1225     +0.2%
-------------------------------------------------------------------------------------------------

Legend:
  Cyan: reference source for comparison. Green: improvement, Red: regression.
  Δ: percentage change from reference source.