[3.14] gh-136428: amend UUIDv8 performance improvements (GH-136903) (#136904)

[3.14] gh-136428: amend UUIDv8 performance improvements (GH-136903) (#136904)

gh-136428: amend UUIDv8 performance improvements (GH-136903)

UUIDv8 has been added in Python 3.14.0a2 and its construction time
has been improved in Python 3.14.0a4, but since those changes will
not be visible when comparing the latest Python 3.13 and 3.14 together,
we do not document them on the What's New page to avoid confusion.
(cherry picked from commit 5798348a0739ccf46f690f5fa1443080ec5de310)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>