Include com.android.runtime in the "runtime" linker namespace.

This is a temporary fix to keep the Bionic-associated libraries accessible
in the runtime namespace, pending a proper namespace split.

Test: Build & boot with taimen_hwasan-userdebug
Bug: 139408016
Bug: 139916951
Exempt-From-Owner-Approval: Approved internally
Change-Id: I27069b20f7c7068b931340f548b284ce1676466c
Merged-In: I27069b20f7c7068b931340f548b284ce1676466c