Issue #14061: Misc fixes and cleanups in archiving code in shutil.

Imporoved the documentation and tests for make_archive() and unpack_archive().
Improved error handling when corresponding compress module is not available.
Brake circular dependency between shutil and tarfile modules.

diff --cc Doc/library/shutil.rst
Simple merge

diff --cc Lib/shutil.py
Simple merge

diff --cc Lib/test/test_shutil.py
index 46e2c57746d2887050133bebe0615c0d185d8f83,709feebf017a25f3e8a259624420f75bfb86981c..2ad3a21c86d2c1bd2813219c2ee3a1a907905b43
--- 1/Lib/test/test_shutil.py
--- 2/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@@ -22,20 -23,7 +23,8 @@@ import zipfil
  import warnings
  
  from test import support
 -from test.support import TESTFN, check_warnings, captured_stdout
 +from test.support import (TESTFN, check_warnings, captured_stdout,
-                           requires_zlib, android_not_root)
- 
- try:
-     import bz2
-     BZ2_SUPPORTED = True
- except ImportError:
-     BZ2_SUPPORTED = False
- 
- try:
-     import lzma
-     LZMA_SUPPORTED = True
- except ImportError:
-     LZMA_SUPPORTED = False
++                          android_not_root)
  
  TESTFN2 = TESTFN + "2"