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

[Nick Desaulniers via llvm-commits]

nickdesaulniers wrote:

```sh
$ bazel query @llvm-project//libc/... --enable_workspace
ERROR: Failed to load Starlark extension '@@rules_cc//cc/toolchains:toolchain_config_utils.bzl'.
Cycle in the workspace file detected. This indicates that a repository is used prior to being defined.
The following chain of repository dependencies lead to the missing definition.
 - @@rules_cc
This could either mean you have to add the '@@rules_cc' repository with a statement like `http_archive` in your WORKSPACE file (note that transitive dependencies are not added automatically), or move an existing definition earlier in your WORKSPACE file.
ERROR: Error computing the main repository mapping: cycles detected during computation of main repo mapping
```

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