[3.13] gh-119342: Fix a potential denial of service in plistlib (GH-119343) (GH-142144)

[3.13] gh-119342: Fix a potential denial of service in plistlib (GH-119343) (GH-142144)

Reading a specially prepared small Plist file could cause OOM because file's
read(n) preallocates a bytes object for reading the specified amount of
data. Now plistlib reads large data by chunks, therefore the upper limit of
consumed memory is proportional to the size of the input file.
(cherry picked from commit 694922cf40aa3a28f898b5f5ee08b71b4922df70)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Origin: backport, https://github.com/python/cpython/commit/71fa8eb8233b37f16c88b6e3e583b461b205d1ba

Gbp-Pq: Name CVE-2025-13837.patch