utils: merge spack.environment into spack.util.environment

- `spack.util.environment` is the new home for routines that modify
  environment variables.

- This is to make room for `spack.environment` to contain new routines
  for dealing with spack environments

var/spack/repos/builtin/packages/foam-extend/package.py

@@ -36,7 +36,7 @@
 import os
 
 from spack import *
-from spack.environment import EnvironmentModifications
+from spack.util.environment import EnvironmentModifications
 from spack.pkg.builtin.openfoam_com import OpenfoamArch
 from spack.pkg.builtin.openfoam_com import add_extra_files
 from spack.pkg.builtin.openfoam_com import write_environ

var/spack/repos/builtin/packages/fsl/package.py

@@ -4,7 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 from spack import *
-from spack.environment import EnvironmentModifications
+from spack.util.environment import EnvironmentModifications
 import os
 
 

var/spack/repos/builtin/packages/openfoam-com/package.py

@@ -43,7 +43,7 @@
 import os
 
 from spack import *
-from spack.environment import EnvironmentModifications
+from spack.util.environment import EnvironmentModifications
 import llnl.util.tty as tty