.circleci: Add filter to run nightly builds on tag (#34078)
Summary:
## What this will do:
When the repository is tagged the current nightly build pipelines will run and upload to the `test` subdirectory in our S3 bucket for `download.pytorch.org`. Will also upload to the correct organization on anaconda [pytorch-nightly](https://anaconda.org/pytorch-test)
This is only meant for release candidates and will actually not run on any tag that does not match the release candidate regex.
This has been tested on a small scale with: https://github.com/seemethere/test-repo/commit/3ebe0ff2f8ae679ac2da6922df7b1b62458f65a2
## Related PRs:
* `.circleci: Divert packages to test channel on tag`: https://github.com/pytorch/pytorch/pull/33842
* `.cirlceci: Swap PYTORCH_BUILD_VERSION if on tag`: https://github.com/pytorch/pytorch/pull/33326
## Work to be done later:
- [ ] Figure out how to remove manual step of updating s3 html indices.
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34078
Differential Revision: D20204104
Pulled By: seemethere
fbshipit-source-id: 685630e8a04b19fc17374585e9228a13a8c3e407
