use Bazelisk to fetch Bazel in CI (#101424)
use Bazelisk to fetch Bazel in CI
Summary:
Advantages:
1. this is cross-platform, no MacOS specific code
2. this lets us use define the version of Bazel succinctly in
.bazelversion (already provided)
Note that this change will upgrade our version of Bazel to 6.1.1.
Test Plan: Rely on CI.
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Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/pytorch/pytorch/pull/101424).
* #101406
* #101405
* #101445
* __->__ #101424
* #101411
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101424
Approved by: https://github.com/huydhn, https://github.com/vors
