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

[Anatoly Trosinenko via llvm-commits]

atrosinenko wrote:

Sorry, I forgot to re-run `clang-format` after fixing compilation error (it is impossible to use overloaded `createBitVector` function both for bits and for ranges, as `createBitVector(Size, {})` would be ambiguous then).

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