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/qorts/package.py

@@ -24,7 +24,6 @@
 ##############################################################################
 from spack import *
 import os.path
-from shutil import copyfile
 
 
 class Qorts(RPackage):
@@ -59,7 +58,7 @@ def install_jar(self):
         # explicitly codes the path for java and the jar file.
         script_sh = join_path(os.path.dirname(__file__), "QoRTs.sh")
         script = self.prefix.bin.QoRTs
-        copyfile(script_sh, script)
+        install(script_sh, script)
         set_executable(script)
 
         # Munge the helper script to explicitly point to java and the