Adopt ci-infrastructure CI

[mcocdawc]

Moves fckit onto the ci-infrastructure CI, on feature/fdb-747-new-cicd so it is built together with ecmwf/metkit#293, ecmwf/eckit#371, ecmwf/eccodes#590 and ecmwf/ecbuild#192.

• .ci/manifest.toml, .ci/build.sh.j2 and CMakePresets.json (ci, and mpi inheriting it).
• Runner legs on the platforms eckit builds in feat(fdb-747): Apply new cicd distro combinations eckit#371, plus a g++-13 mpi leg on the OpenMPI image; HPC hpc-atos-gnu legs default and mpi (load openmpi).
• New ci.yml; the previous one is kept as old_CI.yml with its triggers unchanged.
• Pre-commit with check-ci-approval, its allowlist, actionlint config, contributor-declaration workflow, and the regenerate workflow, whose bot adds the generated cross-repo-trigger*.yml/trigger-downstream*.yml.

Depends on ecbuild and eckit; fckit[mpi] builds against eckit[mpi]. atlas is its downstream ([[trigger-downstream]]).

The mpi legs build against eckit's mpi legs, which are on the same branch in ecmwf/eckit#371.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.07%. Comparing base (346c96a) to head (d5babec).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #107   +/-   ##
========================================
  Coverage    51.07%   51.07%           
========================================
  Files           58       58           
  Lines         4854     4854           
  Branches       453      453           
========================================
  Hits          2479     2479           
  Misses        2375     2375           

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