Add `mallopt` and related constants for Android

[chriswailes]

Description

This change adds constants that can be passed to BIONIC's implementation of mallopt

Sources

Constant definitions in BIONIC source: https://cs.android.com/android/platform/superproject/main/+/main:bionic/libc/include/malloc.h;l=215

Checklist

• [X] Relevant tests in libc-test/semver have been updated
• [X] No placeholder or unstable values like *LAST or *MAX are included
• [X] Tested locally (cd libc-test && cargo test --target mytarget); especially relevant for platforms that may not be checked in CI