Use translate to improve performance of canonicalize_name

Co-Authored-By: Henry Schreiner <henryschreineriii@gmail.com>

Author: hugovk

Lib/importlib/metadata/__init__.py

@@ -890,6 +890,13 @@ def search(self, prepared: Prepared):
         return itertools.chain(infos, eggs)
 
 
+# Translation table for Prepared.normalize: lowercase and replace - . with _
+_normalize_table = str.maketrans(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ-.",
+    "abcdefghijklmnopqrstuvwxyz__",
+)
+
+
 class Prepared:
     """
     A prepared search query for metadata on a possibly-named package.
@@ -925,7 +932,13 @@ def normalize(name):
         """
         PEP 503 normalization plus dashes as underscores.
         """
-        return re.sub(r"[-_.]+", "-", name).lower().replace('-', '_')
+        # Emulates ``re.sub(r"[-_.]+", "-", name).lower()`` from PEP 503
+        # About 3x faster, safe since packages only support alphanumeric characters
+        value = name.translate(_normalize_table)
+        # Condense repeats (faster than regex)
+        while "__" in value:
+            value = value.replace("__", "_")
+        return value
 
     @staticmethod
     def legacy_normalize(name):