optimized-routines-mem: Share with bionic

Migrate the libc dependencies for Rust to Bionic but keep using this
library as a back-end for arm64 so update the visibility to point to
libc instead of client code directly.

Test: m pvmfw_bin && atest vmbase_example.integration_test
Change-Id: I0e8b2ef862fcb47fcb66494aa180a7e66575a0a7