[libc++] Encode the standard version in the ABI tag (#218527)

This prevents ODR mismatch issues from biting us across standard
versions. The order of elements in the ABI tag is now: libc++ version,
hardening mode, assertion semantic, exceptions, standard version.

Fixes #218524

GitOrigin-RevId: d5f6c302fff1aeed8fb6a247c21a694b156778bc