refactor: decouple sys_exit_type with dsn_runtime

[levy5307]

There are some types which are defined in dsn_runtime being used in global_config.h, so this file is coupled with dsn_runtime. And now sys_exit_type is defined in this file. So if you want to use sys_exit_type, you must coupled with dsn_runtime, which is not what we want. So in this pull request, I put sys_exit_type to a seperated file.
And remove the include of global_config.h in include/dsn/tool_api.h, which is widely included in rdsn.

[neverchanje]

sys_exit_type is related to dsn::tools::sys_exit (in include/dsn/tool_api.h), which manages the hooks for system exit.

DSN_API extern join_point<void, sys_exit_type> sys_exit;

NORETURN DSN_API void dsn_exit(int code)
{
    printf("dsn exit with code %d\n", code);
    fflush(stdout);
    ::dsn::tools::sys_exit.execute(::dsn::SYS_EXIT_NORMAL);

    _exit(code);
}

You can move sys_exit_type with sys_exit to a file called include/dsn/sys_exit_hook.h to make the relationship clear.

[levy5307]

sys_exit_type is related to dsn::tools::sys_exit (in include/dsn/tool_api.h), which manages the hooks for system exit.

DSN_API extern join_point<void, sys_exit_type> sys_exit;

NORETURN DSN_API void dsn_exit(int code)
{
    printf("dsn exit with code %d\n", code);
    fflush(stdout);
    ::dsn::tools::sys_exit.execute(::dsn::SYS_EXIT_NORMAL);

    _exit(code);
}

You can move sys_exit_type with sys_exit to a file called include/dsn/sys_exit_hook.h to make the relationship clear.

Done.