Refactor utils into separate modules.

lib/spack/spack/arch.py

lib/spack/spack/cmd/test.py

lib/spack/spack/compilers/__init__.py

lib/spack/spack/globals.py

lib/spack/spack/package.py

lib/spack/spack/packages/__init__.py

lib/spack/spack/url.py

lib/spack/spack/util/__init__.py

lib/spack/spack/util/compression.py

lib/spack/spack/util/environment.py

lib/spack/spack/util/executable.py

lib/spack/spack/util/filesystem.py

lib/spack/spack/util/lang.py

lib/spack/spack/validate.py