[llvm] [bazel] update .bazelversion to 8.0.0 (PR #119425)

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

> build is still red, now due to #114333 and [9735873](https://github.com/llvm/llvm-project/commit/9735873009ca86b03c3283d06edd1b3a190d4af9). Am I also on the hook to fix those? :^)

I'm looking at the MLIR one now, will get the LLDB one next.

https://github.com/llvm/llvm-project/pull/119425