Add builtin function __builtin_get_device_side_mangled_name
to get device side manged name for functions and global
variables, which can be used to get symbol address of kernels
or variables by mangled name in dynamically loaded
bundled code objects at run time.
Reviewed by: Artem Belevich
Differential Revision: https://reviews.llvm.org/D99301
Yaxun (Sam) Liu