Update version numbers for TensorFlow 2.12.0-rc0
Before merging this PR, please double check that it has correctly updated
`core/public/version.h`, `tools/pip_package/setup.py`, and
`tensorflow/tensorflow.bzl`. Also review the execution notes below:

```
Major: 2 -> 2
Minor: 12 -> 12
Patch: 0 -> 0

WARNING: Below are potentially instances of lingering old version string 
"2.12.0" in source directory "tensorflow/" that are not updated by this script. 
Please check them manually!
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:32:2.12.0
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:33:2.12.0
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:34:2.12.0
tensorflow/tools/ci_build/release/requirements_mac.txt:4:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:28:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:29:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:30:2.12.0
tensorflow/tools/pip_package/setup.py:50:2.12.0
tensorflow/tools/pip_package/setup.py:127:2.12.0
tensorflow/tools/pip_package/setup.py:128:2.12.0
tensorflow/tools/pip_package/setup.py:130:2.12.0
tensorflow/tools/pip_package/redundant_tf_nightly_gpu/setup.cfg:17:2.12.0
tensorflow/tools/pip_package/redundant_tensorflow_gpu/setup.cfg:17:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:183:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:191:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:315:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:355:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:360:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:397:2.12.0
tensorflow/lite/core/c/c_api.h:115:2.12.0
tensorflow/tensorflow.bzl:73:2.12.0

WARNING: Below are potentially instances of lingering old version string 
"2.12.0" in source directory "tensorflow/" that are not updated by this script. 
Please check them manually!
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:32:2.12.0
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:33:2.12.0
tensorflow/tools/tf_sig_build_dockerfiles/devel.requirements.txt:34:2.12.0
tensorflow/tools/ci_build/release/requirements_mac.txt:4:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:28:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:29:2.12.0
tensorflow/tools/ci_build/release/requirements_common.txt:30:2.12.0
tensorflow/tools/pip_package/setup.py:50:2.12.0
tensorflow/tools/pip_package/setup.py:127:2.12.0
tensorflow/tools/pip_package/setup.py:128:2.12.0
tensorflow/tools/pip_package/setup.py:130:2.12.0
tensorflow/tools/pip_package/redundant_tf_nightly_gpu/setup.cfg:17:2.12.0
tensorflow/tools/pip_package/redundant_tensorflow_gpu/setup.cfg:17:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:183:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:191:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:315:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:355:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:360:2.12.0
tensorflow/lite/tools/versioning/runtime_version.cc:397:2.12.0
tensorflow/lite/core/c/c_api.h:115:2.12.0
tensorflow/tensorflow.bzl:73:2.12.0
```