Remove unused public headers from FastCaloSimHit package.

John Derek Chapmanrequested to merge
jchapman/athena:FastCaloSimHit_cleanup_main into main

Following on from !67026 (merged), !67187 (merged), !67189 (merged). Removing unused public headers from the FastCaloSimHit package and converting it to be a pure component library. Also removing FastCaloSimHitLib from the dependencies of other packages.

Tagging @mduehrss, @jbeirer, @zhangr, @cyoung

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