stubRoutines.hpp is unnecessarily included by thread.hpp and copy.hpp. This causes a large number of header files related to native code generation to be included by almost all HotSpot .o files.

https://github.com/openjdk/jdk/blob/f0b1194004a6e7ebcb918cf58bad16f68130ccf2/src/hotspot/share/runtime/thread.hpp#L44
https://github.com/openjdk/jdk/blob/f0b1194004a6e7ebcb918cf58bad16f68130ccf2/src/hotspot/share/utilities/copy.hpp#L28

Before the fix, stubRoutines.hpp is included by 803 .o files.
After the fix, stubRoutines.hpp is included by 117 .o files.

The total number of included header files decreased from 252893 to 247631, or about 2%.