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.

share/spack/qa/flake8_formatter.py

@@ -1,7 +1,8 @@
 import re
 import sys
-import pycodestyle
 from collections import defaultdict
+
+import pycodestyle
 from flake8.formatting.default import Pylint
 from flake8.style_guide import Violation