git: openjdk/loom: fibers: Add assertions

[duke]

Changeset: 3cd4fb4d
Author:    Ron Pressler <ron.pressler at oracle.com>
Date:      2021-07-30 18:42:40 +0000
URL:       https://git.openjdk.java.net/loom/commit/3cd4fb4daa13a58b259a589b853ff08a0af81816

Add assertions

! src/hotspot/share/prims/jvmtiEnvBase.cpp
! src/hotspot/share/runtime/registerMap.hpp
! src/hotspot/share/runtime/vframe.cpp