ci : add coreml job that converts base.en to coreml [no ci] (#2981)

ci : add coreml job that converts base.en to coreml [no ci] (#2981)

* ci : add coreml job that converts base.en to coreml [no ci]

This commit adds a new job to the CI pipeline that downloads the base.en
model and converts it to CoreML format. The CoreML model is then packed
into a zip file and uploaded as an artifact.

This will only be done for pushes to master, releases, or pre-releases.

Refs: https://github.com/ggerganov/whisper.cpp/issues/2783

* coreml : remove publishing of coreml model

* ci : add GGML_OPENMP=OFF to ubuntu-22-gcc-sanitized