Move th->altstack to th->nt->altstack.

`NON_SCALAR_THREAD_ID` shows `pthread_t` is non-scalar (non-pointer)
and only s390x is known platform. However, the supporting code is
very complex and it is only used for deubg print information.

So this patch removes the support of `NON_SCALAR_THREAD_ID`
and make the code simple.

caller should check the result of `native_tls_get()`.

Thread-local storage is supported since Mac OS X 10.7.  Enable TLS
only when the target version is enough.

`rb_thread_t` contained `native_thread_data_t` to represent
thread implementation dependent data. This patch separates
them and rename it `rb_native_thread` and point it from
`rb_thraed_t`.

Now, 1 Ruby thread (`rb_thread_t`) has 1 native thread (`rb_native_thread`).

Now GVL is not process *Global* so this patch try to use
another words.

* `rb_global_vm_lock_t` -> `struct rb_thread_sched`
  * `gvl->owner` -> `sched->running`
  * `gvl->waitq` -> `sched->readyq`
* `rb_gvl_init` -> `rb_thread_sched_init`
* `gvl_destroy` -> `rb_thread_sched_destroy`
* `gvl_acquire` -> `thread_sched_to_running` # waiting -> ready -> running
* `gvl_release` -> `thread_sched_to_waiting` # running -> waiting
* `gvl_yield`   -> `thread_sched_yield`
* `GVL_UNLOCK_BEGIN` -> `THREAD_BLOCKING_BEGIN`
* `GVL_UNLOCK_END` -> `THREAD_BLOCKING_END`

* removed
  * `rb_ractor_gvl`
  * `rb_vm_gvl_destroy` (not used)

There are GVL functions such as `rb_thread_call_without_gvl()` yet
but I don't have good name to replace them. Maybe GVL stands for
"Greate Valuable Lock" or something like that.

* Prefixed ccan headers

* Remove unprefixed names in ccan/build_assert

* Remove unprefixed names in ccan/check_type

* Remove unprefixed names in ccan/container_of

* Remove unprefixed names in ccan/list

Co-authored-by: Samuel Williams <samuel.williams@oriontransfer.co.nz>

* See [Feature #17752]

Co-authored-by: xtkoba (Tee KOBAYASHI) <xtkoba+ruby@gmail.com>