install_tree, copy_tree can install into existing directory structures (#8289)

Replace use of `shutil.copytree` with `copy_tree` and `install_tree` functions in `llnl.util.filesystem`.

- `copy_tree` copies without setting permissions.  It should be used to copy files around in the build directory.
- `install_tree` copies files and sets permissions.  It should be used to copy files into the installation directory.
- `install` and `copy` are analogous single-file functions.
- add more extensive tests for these functions
- update packages to use these functions.

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

@@ -25,7 +25,6 @@
 #
 # Author: Justin Too <too1@llnl.gov>
 #
-import distutils.dir_util
 from spack import *
 
 
@@ -72,7 +71,7 @@ def url_for_version(self, version):
         return url.format(version, minor_version)
 
     def install(self, spec, prefix):
-        distutils.dir_util.copy_tree(".", prefix)
+        install_tree('.', prefix)
 
     def setup_environment(self, spack_env, run_env):
         run_env.set('JAVA_HOME', self.spec.prefix)