[llvm] [ADT] BitVector: give `subsetOf(RHS)` name to `!test(RHS)` (NFC) (PR #170875)

[Anatoly Trosinenko via llvm-commits]

atrosinenko wrote:

* **#170876** <a href="https://app.graphite.com/github/pr/llvm/llvm-project/170876?utm_source=stack-comment-icon" target="_blank"><img src="https://static.graphite.dev/graphite-32x32-black.png" alt="Graphite" width="10px" height="10px"/></a>
* **#170875** <a href="https://app.graphite.com/github/pr/llvm/llvm-project/170875?utm_source=stack-comment-icon" target="_blank"><img src="https://static.graphite.dev/graphite-32x32-black.png" alt="Graphite" width="10px" height="10px"/></a> 👈 <a href="https://app.graphite.com/github/pr/llvm/llvm-project/170875?utm_source=stack-comment-view-in-graphite" target="_blank">(View in Graphite)</a>
* `main`


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https://github.com/llvm/llvm-project/pull/170875