[3.12] gh-75171: Fix parsing invalid email address headers starting or ending with a dot (GH-15600) (GH-117964)

(cherry picked from commit 8cc9adbfddc8e37cf7d621b12754eecb0584f5da)

Co-authored-by: tsufeki <tsufeki@ymail.com>
Co-authored-by: Tim Bell <timothybell@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>