bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391) (#25249)

Fix Regular Expression Denial of Service (ReDoS) vulnerability in
urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex
has quadratic worst-case complexity and it allows cause a denial of
service when identifying crafted invalid RFCs. This ReDoS issue is on
the client side and needs remote attackers to control the HTTP server.
(cherry picked from commit 7215d1ae25525c92b026166f9d5cac85fb1defe1)

Co-authored-by: Yeting Li <liyt@ios.ac.cn>