Updated testing, documentation and fixes

• Testing: expanded array of CI tests to include
  • gfortran {12,13,14} on ubuntu-24.04, macos-13-x86_64, macos-14-arm64
  • flang {19.1.1,20.1.0} on ubuntu-24.04
  • ifx 2025.{0.0,1.0} on ubuntu-24.04
• Building:
  • Removed redundant and unneeded information in fpm.toml
  • Fixed the error termination tests to be compatible with ifx
• Documentation: updated gfortran build commands and fixed typos
• Fix: better parallel call-backs to support Caffeine, issue #57

Pull requests merged in this release

• CI expansion in GitHub Actions by @bonachea in #54
• Fixes for Intel oneAPI 2025 by @bonachea in #55
• doc(README): update compiler commands/versions by @bonachea in #53
• Fix parallel callbacks feature by @bonachea in #58
• Reduce the manifest by @rouson in #60

Full Changelog: 2.1.0...2.1.2