[NFC][msan][test] Increase allocation size in release_origin.c (#228333)

On systems with many CPUs and 64 KiB pages (such as 192-CPU ppc64le on
`sanitizer-ppc64le-linux`), the kernel per-CPU RSS counter batch size
(24 MiB) exceeds the 20 MiB allocation in this test, so /proc/self/statm
may not reflect the RSS changes. Increase the allocation size to 100 MiB
and adjust the soft RSS limits accordingly.

Assisted-by: Gemini
GitOrigin-RevId: eb37e16f2de1d55106f5928e63eb92d4d40e2a66