Refactor mechanisms of building TF wheel and storing TF project version.

This change introduces a uniform way of building the TF wheel and controlling the filename version suffixes.

A new repository rule `python_wheel_version_suffix_repository` provides information about project and wheel version suffixes. The final value depends on environment variables passed to Bazel command: `_ML_WHEEL_WHEEL_TYPE, _ML_WHEEL_BUILD_DATE, _ML_WHEEL_GIT_HASH, _ML_WHEEL_VERSION_SUFFIX`

`tf_version.bzl` defines the TF project version and loads the version suffix information calculated by `python_wheel_version_suffix_repository`.

The targets `//tensorflow/core/public:release_version, //tensorflow:tensorflow_bzl //tensorflow/tools/pip_package:setup_py` use the version chunks defined above.

The version of the wheel in the build rule output depends on the environment variables.

Environment variables combinations for creating wheels with different versions:
  * snapshot (default build rule behavior): `--repo_env=ML_WHEEL_TYPE=snapshot`
  * release: `--repo_env=ML_WHEEL_TYPE=release`
  * release candidate: `--repo_env=ML_WHEEL_TYPE=release --repo_env=ML_WHEEL_VERSION_SUFFIX=-rc1`
  * nightly build with date as version suffix: `--repo_env=ML_WHEEL_TYPE=nightly --repo_env=ML_WHEEL_BUILD_DATE=<YYYYmmdd>`
  * build with git data as version suffix: `--repo_env=ML_WHEEL_TYPE=custom --repo_env=ML_WHEEL_BUILD_DATE=$(git show -s --format=%as HEAD) --repo_env=ML_WHEEL_GIT_HASH=$(git rev-parse HEAD)`

PiperOrigin-RevId: 733444080

Author: tensorflower-gardener

Diff for: site/en/install/source.md

@@ -39,7 +39,7 @@ environment, omit the `--user` argument):
 
 Note: A `pip` version >19.0 is required to install the TensorFlow 2 `.whl`
 package. Additional required dependencies are listed in the
-<a href="https://github.com/tensorflow/tensorflow/blob/master/tensorflow/tools/pip_package/setup.py" class="external"><code>setup.py</code></a>
+<a href="https://github.com/tensorflow/tensorflow/blob/master/tensorflow/tools/pip_package/setup.py.tpl" class="external"><code>setup.py.tpl</code></a>
 file under `REQUIRED_PACKAGES`.
 
 ### Install Bazel