gh-91719: Add pycore_opcode.h internal header file (#91906)

Move the following API from Include/opcode.h (public C API) to a new
Include/internal/pycore_opcode.h header file (internal C API):

* EXTRA_CASES
* _PyOpcode_Caches
* _PyOpcode_Deopt
* _PyOpcode_Jump
* _PyOpcode_OpName
* _PyOpcode_RelativeJump
11 files changed