ArchSpec: minor cleanup of a few methods (#26376)
ArchSpec: minor cleanup of a few methods (#26376)

* Remove vestigial code to be compatible with Spack v0.9.X
* ArchSpec: reworked __repr__ to be more adherent to common Python idioms
* ArchSpec: simplified __init__.py and copy()
LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack