Update PyTorch and XLA pin. (#9668)

This PR updates the following pins:

- PyTorch:
pytorch/pytorch@928ac57
to
pytorch/pytorch@21fec65
(v2.9.0-rc5)
- OpenXLA:
openxla/xla@92f7b59
to
openxla/xla@9a9aa0e
- `libtpu`: 0.0.21 to 0.0.24
- JAX (and `jaxlib`): 0.7.1 to 0.8.0

**Key Changes:**

- `@python` was replaced by `@rules_python` at `BUILD` file (ref:
[jax-ml/jax#31709](jax-ml/jax#31709))
- `TF_ATTRIBUTE_NORETURN` was removed in favor of abseil (ref:
[openxla/xla#31699](openxla/xla#31699))
- Replaced include of `xla/pjrt/tfrt_cpu_pjrt_client.h` file by
`xla/pjrt/cpu/cpu_client.h` in `pjrt_registry.cpp`
([openxla/xla#30936](openxla/xla#30936))
- Moved the old `xla/tsl/platform/default/logging.*` to
`torch_xla/csrc/runtime/tsl_platform_logging.*`
- They were removed in
[openxla/xla#29477](openxla/xla#29477)
- Copied them here, temporarily. They should be removed once we update
our error throwing macros.
- Commented out a few macro definitions, avoiding macro re-definitions

**Update (Oct 3):**
- Add an OpenXLA patch for fixing `static_assert(false)` for GCC < 13
([ref](https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=9944ca17c0766623bce260684edc614def7ea761))
- Removed the `flax` pin, since it does not overwrite `jax` anymore
- Removed `TPU*` prefix of `jax.experimental.pallas.tpu` components
(ref: [jax-ml/jax#29115](jax-ml/jax#29115))

---------

Co-authored-by: Bhavya Bahl <bbahl@google.com>

Update readme for 2.8.1 branch (#9627)

Add manylinux for pytorch/xla

Add flags for size optimization (#9547)

cherry-pick: make jax as optional dependency (#9530)

Update libtpu and jax versions to use with release (#9526)

Update README.md

Update tests CI for r2.8 (#9426)

support manylinux build (#9035)

Fix 3.9 Python syntax (#9018)