PI: Don't load entire file into memory when passed file name

This halves allocated memory when doing a simple
PdfWriter(clone_from=«str»)

Author: mjsir911

pypdf/_reader.py

@@ -47,6 +47,7 @@
     Union,
     cast,
 )
+import weakref
 
 from ._encryption import Encryption, PasswordType
 from ._page import PageObject, _VirtualList
@@ -310,9 +311,11 @@ def __init__(
                 "It may not be read correctly.",
                 __name__,
             )
+
         if isinstance(stream, (str, Path)):
-            with open(stream, "rb") as fh:
-                stream = BytesIO(fh.read())
+            stream = open(stream, "rb")
+            self._finalizer = weakref.finalize(self, stream.close)
+
         self.read(stream)
         self.stream = stream