Prepare FAIRChem Hydra entry points for Hydra 1.4

[Copilot]

Hydra 1.4 deprecates legacy version_base values and tightens config filename handling, which breaks FAIRChem’s primary CLI startup path and risks unbounded dependency resolution. This PR updates Hydra compatibility in fairchem-core and adds focused coverage for Hydra composition/startup paths that previously had no direct tests.

• Hydra compatibility in core CLI

  • Updated src/fairchem/core/_cli.py to use version_base="1.3" (from "1.1").
  • Preserved existing .yml user configs under Hydra 1.4 by composing from a temporary .yaml copy when needed.

• Dependency floor for upcoming Hydra release

  • Updated packages/fairchem-core/pyproject.toml:
    • hydra-core → hydra-core>=1.3

• Hydra-path coverage added where missing

  • Added tests/core/scripts/test_sweep_inference_benchmark.py to validate load_config() composition and JobConfig initialization.
  • Extended tests/lammps/test_lammps_fc.py with a Hydra entrypoint startup test for lammps_fc.main() using lightweight mocking of runtime LAMMPS execution.

# src/fairchem/core/_cli.py
with hydra.initialize_config_dir(config_directory, version_base="1.3"):
    cfg = hydra.compose(config_name=config_name, overrides=overrides_args)

# For legacy .yml configs under Hydra 1.4:
# write temp <name>.yaml and compose from that file

• Fixes Prepare FAIRChem for Hydra 1.4 #2130