Add release-ready envs and new grouped upload configuration 
Ok -- how about this? I thoroughly tidied everything up. Now, every job config will be a combination of multiple env files. I updated the instructions to indicate this. Running a TensorFlow job locally is now possible in a one-liner, like:

```
TFCI=py311,linux_x86,multicache ci/official/wheel.sh
```

I'm pretty sure this still works just fine for all of our special cases, which can be handled with either conditionals in the code (like with the MacOS Python 3.11 differences) or extra envs to add to the CI jobs. 

Note: All the CI jobs will fail because the way of specifying TFCI= has changed. After review, I'll have to import this PR manually and update our CI jobs in the same CL to reflect this new method. I think I already handled the merge conflicts to pull in the latest job state (I'll add Nitin for internal review once the CL gets created).
This is another big cleanup of envs:

- Rewrote TFCI variable settings as combinations of other TFCI variables
- Created "upload.sh" and new `TFCI_ARTIFACT_...` variables.
   - Every script execution in a pipeline (i.e. all of the day's platform-specific tf-nightly jobs) will be given a pipeline-specific parameter such that every build artifact for a pipeline's jobs will go to one GCS bucket.
   - At the end of the pipeline, `upload.sh` will fetch every artifact from the current pipeline and uploads them to PyPI and TensorFlow's public GCS bucket.
   - I'm planning for the layout to be `gs://tensorflow/(nightly|release)/VERSION/`, with  `gs://tensorflow/nightly/latest` pointing to the most recent nightly and `gs://tensorflow/release/latest` for the latest release. One-folder-per-version is a huge simplification of the way packages are uploaded today, and should help keep upload-maintenance simple.
- Added `ci_version` envs which can expose TF version strings, sourced from the canonical sources, to the scripts if explicitly sourced. Currently only used by upload.sh, but may be useful for more later.

- [x] I still need to fix any.sh, bisect.sh, and a couple other places that referenced the old TFCI method