[3.8] bpo-39667: Sync zipp 3.0 (GH-18540) (GH-18701)

* bpo-39667: Sync zipp 3.0 (GH-18540)

* bpo-39667: Improve pathlib.Path compatibility on zipfile.Path and correct performance degradation as found in zipp 3.0

* 📜🤖 Added by blurb_it.

* Update docs for new zipfile.Path.open

* Rely on dict, faster than OrderedDict.

* Syntax edits on docs

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
(cherry picked from commit 0aeab5c4381f0cc11479362af2533b3a391312ac)

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>

* Clarify the change in behavior with a couple of workaround options.

* Restore API compatibility while backporting performance improvements.

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 5dc6516..07faacc 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -17,7 +17,6 @@
 import threading
 import time
 import contextlib
-from collections import OrderedDict
 
 try:
     import zlib # We may need its compression method
@@ -2125,24 +2124,6 @@
         return (fname, archivename)
 
 
-def _unique_everseen(iterable, key=None):
-    "List unique elements, preserving order. Remember all elements ever seen."
-    # unique_everseen('AAAABBBCCDAABBB') --> A B C D
-    # unique_everseen('ABBCcAD', str.lower) --> A B C D
-    seen = set()
-    seen_add = seen.add
-    if key is None:
-        for element in itertools.filterfalse(seen.__contains__, iterable):
-            seen_add(element)
-            yield element
-    else:
-        for element in iterable:
-            k = key(element)
-            if k not in seen:
-                seen_add(k)
-                yield element
-
-
 def _parents(path):
     """
     Given a path with elements separated by
@@ -2184,6 +2165,18 @@
         path, tail = posixpath.split(path)
 
 
+_dedupe = dict.fromkeys
+"""Deduplicate an iterable in original order"""
+
+
+def _difference(minuend, subtrahend):
+    """
+    Return items in minuend not in subtrahend, retaining order
+    with O(1) lookup.
+    """
+    return itertools.filterfalse(set(subtrahend).__contains__, minuend)
+
+
 class CompleteDirs(ZipFile):
     """
     A ZipFile subclass that ensures that implied directories
@@ -2193,13 +2186,8 @@
     @staticmethod
     def _implied_dirs(names):
         parents = itertools.chain.from_iterable(map(_parents, names))
-        # Deduplicate entries in original order
-        implied_dirs = OrderedDict.fromkeys(
-            p + posixpath.sep for p in parents
-            # Cast names to a set for O(1) lookups
-            if p + posixpath.sep not in set(names)
-        )
-        return implied_dirs
+        as_dirs = (p + posixpath.sep for p in parents)
+        return _dedupe(_difference(as_dirs, names))
 
     def namelist(self):
         names = super(CompleteDirs, self).namelist()