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/hdf5-blosc/package.py

@@ -34,13 +34,13 @@ def _install_shlib(name, src, dst):
     if sys.platform == "darwin":
         shlib0 = name + ".0.dylib"
         shlib = name + ".dylib"
-        shutil.copyfile(join_path(src, shlib0), join_path(dst, shlib0))
+        install(join_path(src, shlib0), join_path(dst, shlib0))
         os.symlink(shlib0, join_path(dst, shlib))
     else:
         shlib000 = name + ".so.0.0.0"
         shlib0 = name + ".so.0"
         shlib = name + ".dylib"
-        shutil.copyfile(join_path(src, shlib000), join_path(dst, shlib000))
+        install(join_path(src, shlib000), join_path(dst, shlib000))
         os.symlink(shlib000, join_path(dst, shlib0))
         os.symlink(shlib0, join_path(dst, shlib))