Fix -Wconversion warnings in runtime code

Warnings coming from code in the runtime directory counts.

21 src/hotspot/share/runtime/java.cpp
16 src/hotspot/share/runtime/objectMonitor.hpp
12 src/hotspot/share/runtime/relocator.cpp
11 src/hotspot/share/runtime/sharedRuntime.cpp
10 src/hotspot/share/runtime/arguments.cpp
6 src/hotspot/share/runtime/synchronizer.cpp
6 src/hotspot/share/runtime/deoptimization.cpp
6 src/hotspot/share/runtime/continuationFreezeThaw.cpp
3 /scratch/cphillim/hg/22os-conversion/test/hotspot/gtest/runtime/test_os.cpp
2 /scratch/cphillim/hg/22os-conversion/test/hotspot/gtest/runtime/test_stubRoutines.cpp
2 src/hotspot/share/runtime/thread.cpp
2 src/hotspot/share/runtime/signature.cpp
2 src/hotspot/share/runtime/javaThread.cpp
1 src/hotspot/share/runtime/vmStructs.cpp
1 src/hotspot/share/runtime/vframeArray.cpp
1 src/hotspot/share/runtime/trimNativeHeap.cpp
1 src/hotspot/share/runtime/timer.cpp
1 src/hotspot/share/runtime/threadHeapSampler.cpp
1 src/hotspot/share/runtime/stubRoutines.cpp
1 src/hotspot/share/runtime/statSampler.cpp
1 src/hotspot/share/runtime/safepoint.cpp
1 src/hotspot/share/runtime/os.cpp