[BE] Speedup bazel builds (#105347)
The way it was setup before this PR are that results of `build` step are discarded and are repeated anew during the test step, that was executed in a new pristine container instance.
Avoid that by running builds and tests in the same container instance, that is passed from `Build` to `Test` step via `GITHUB_ENV` variable.
Test plan: [linux-bionic-cpu-py3.10-gcc9-bazel-test](https://github.com/pytorch/pytorch/actions/runs/5578973087/jobs/10193974290#logs) finishes in 27 min instead of 40 min on trunk and [linux-focal-cuda12.1-py3.10-gcc9-bazel-test](https://github.com/pytorch/pytorch/actions/runs/5578973087/jobs/10193975032#logs) finsihes in 44 min instead of 90 min on trunk.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105347
Approved by: https://github.com/huydhn
