imports: sort imports everywhere in Spack (#24695)

* fix remaining flake8 errors

* imports: sort imports everywhere in Spack

We enabled import order checking in #23947, but fixing things manually drives
people crazy. This used `spack style --fix --all` from #24071 to automatically
sort everything in Spack so PR submitters won't have to deal with it.

This should go in after #24071, as it assumes we're using `isort`, not
`flake8-import-order` to order things. `isort` seems to be more flexible and
allows `llnl` mports to be in their own group before `spack` ones, so this
seems like a good switch.

var/spack/repos/builtin.mock/packages/multimethod/package.py

@@ -5,9 +5,8 @@
 
 from six import string_types
 
-from spack import *
 import spack.architecture
-
+from spack import *
 from spack.pkg.builtin.mock.multimethod_base import MultimethodBase