x86-64: Test strlen and wcslen with 0 in the RSI register [BZ #28064]

commit 6f573a27
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Wed Jun 23 01:19:34 2021 -0400

    x86-64: Add wcslen optimize for sse4.1

added wcsnlen-sse4.1 to the wcslen ifunc implementation list.  Since the
random value in the the RSI register is larger than the wide-character
string length in the existing wcslen test, it didn't trigger the wcslen
test failure.  Add a test to force 0 into the RSI register before calling
wcslen.

(cherry picked from commit a6e7c374)